Novice Question: Dedicated Streamers

Basically, I’m confused as to what function a stand-alone music streamer without onboard storage serves.  I know I’ve got some sort of glaring, mental blank spot about this.....the only thing I can figure is that there is some sort of enhanced music file processing over what one gets with most home computers and storage happens by plugging an external storage drive(s) to this sort of component??  Can someone enlighten me better about these?  The Blue Sound “Vault” has caught my eye of late but I’m wondering if I might be missing something by not looking at the “node” by the same company.  I don’t anticipate ever using any sort of music subscription service if this is important...  
Hi OP,
Yep, so streamers usually rely on you either having some music storage on your home network already, or subscribing to a service like Pandora, Tidal, Spotify, etc. There are several home back up / network storage solutions that can function as the source, as well as your average PC. You could also build one out of a Raspberry Pi and a USB stick.

Some streamers include a USB connector to allow you to connect a storage device.
A music streamer is simply a computer program that reads music file data from some source and writes it to a target, typically a DAC. Dacs are the components responsible for converting the digital data to analog. There is usually some user interface provided to select the source of music on the streamer. Streamers generally must be fast enough to stream the music file data in real time. Streaming higher resolution music file data accurately is more challenging accordingly. 
The Bluesound Vault is just that, a way to store your music, and then play it.
The Node is just a way to stream music, be it from a streaming service or from you computer. With multiple units, it can also connect with each other so you can listen in different rooms.
All the iterations of the Nodes are pretty much the same. Only the newest one will allow you to use the 5ghz wifi band. I own the original Node and added a Netgear wireless router to use the 5ghz band.
The nice thing with Bluesound is that you can use an outboard DAC. 
The one that comes with the Node isn't bad, but upgrading to, say, an Ayre Codex or a Schiit Gungnir or Yggrisil will get you pretty far in the Digital streaming mode.
I never thought of using digital streaming, but once I found Spotify, Tidal and Quobuz, I haven't cracked a CD case for 4 years.
I haven’t cracked open a cd case in over 10 years, unless it was to rip it to a hard drive. I had a $3000 CD player from Classe back then and sold it. Back then, a Mac running pure music or amarra was the ticket. Then Audirvana came out. Went the dedicated music server route for a couple of years sharing a large multi TB disk system from a computer and got rid of that because it was still using the flawed USB interface. Now, back to using a computer running Roon server and using a hard wired CAT7 cabling network to interface with my dac with a network bridge card.
if you want to buy a dedicated music server, you are still buying a computer, probably using Linux, which is a great OS but most audiophiles or local technicians have no idea how to work on it. 

Like Lg1 I am somewhat confused about the benefits of a music streamer. What for example is the difference say between a non storage streamer and a Bluetooth receiver such as a Bludento BLT-HD or an Auris bluMe HD? 
Check  out the Music Vault by Sound Science.  You guys are missing the boat
Thanks all and definitely appreciate your inquiry, Mazian as I suppose my confusion about these components may have similarities...  Right now, I’ve got iTunes on my Mac playing 16 bit AIFF ripped from CDs going wirelessly to an Apple Express which goes straight into my integrated amp with no further DAC presence.  While the original question I posted about Streamers without onboard storage has been cleared up somewhat in my mind, I keep wondering what I’d gain by acquiring one of them up and above what I’ve got in terms of functionality (I assume the SQ stands to be possibly be improved significantly? or not?). I suppose a solution like the Vault, with its onboard storage, would save wear and tear on the Mac but to a cost effective degree??  Perhaps the Node 2i plus a TB external drive with a copy of my iTunes collection might be more cost effective in that regard?  Intriguing to ponder, for sure...
My practical experience adding to the above:

8 years ago I ripped all my CDs and started streaming them from iTunes. Shortly after I discovered Spotify and stopped streaming my own CDs and did Spotify instead as Spotify also provided access to all the music that I did not own. After some time I tested Tidal and found out that the quality was better and moved to Tidal, where I am now.

Then I wanted to stream to my HiFi and not just from my computer. I wanted to use my phone as remote controller. Hence, I looked for a streamer that I could connect to my amplifier. Initially I decided for a cheap solution from german Raumfeld and a cheap DAC from Musical Fidelity - to try things out. That worked perfect.

I learned about Roon and realized that provides a lot of information about the bands and albums that I wanted. Hence, I upgraded my streamer to a Roon Ready streamer, where I have Roon and Tidal (Innuos Zen mini).

Next was upgrading my DAC, where I was in doubt whether to select an MQA enabled or not. I finally decided for a non-MQA called RME ADI-2 DAC.

As part of the process I have upgraded my Ethernet and USB cable.

Good luck with your journey ahead.
I find it useful to use the computer terminology:

Storage: where the music files are stored

Music server: software, running on a pc, that catalogues music available in networked or local storage and offers it up to a control point with various sorting options. 

Control point: software, on a phone, iPad, or even a renderer, that sees a music server, and allows you to choose what to play, and which renderer to send it to. 

Renderer: receives a music file from a music server or streaming service and delivers it to a DAC

streamers are usually a combination of renderer and control point, although most allow you to use your phone/iPad as a control point. 

There are many proprietary standards (Like BlueOs) but most servers/control points/ renderers will inter-operate on a communication standard called DLNA/UPnP.  

I’m a bit of an open-source junkie, so I run minimserver music server software on network-attached storage. I run BubbleUPnP on an android tablet as a control point, and I have cambridge, iFI, KEF LS50W and Chromecast renderers/streamers to which I can send output.  Bubble sees my tidal and Qobuz accounts as well as my music server so it can see all my music sources and renderer endpoints. You may have heard of Roon, which is a very popular combination music server and control point software that does all the same stuff, but requires that your streamer be a Roon endpoint. Slightly less common than UPnP compliance. 

It is a a lot of terminology, but one walk through of an existing setup and you will totally get it. 
@ahofer laid it out really well.  I like to think of these in a few buckets:

-  DAC with streamer functionality, has digital+network in, digital+analog out  (Auralic, MSB, NAD, others)
-  Streamer with DAC functionality, has network in, digital+analog out (Lumin, others)
-  Streamers, has network in and digital out, needs external DAC (Lumin, Auralic, Sonore, others)
-  Network Music Server and Streamer, has digital out (Aurender, others)
- Network Music Server, Streamer, and DAC (Aurender, others)

There are also computer based network severs which can have DACS.  These usually have specialized hardware, like linear power supplies, around computer parts (Innuos, Roon).

Also there is just software solutions that can be installed on your computer at home which can act as a server. (Roon, others)

The theory behind this is is that the more specialized the component the better the sound.  Each will have a different interface and mobile app to go with it.  Some share compatible with Roon, mostly as an endpoint.

This isn’t all inclusive of all solutions, but hope it helps.
If you're streaming music through your MAC or computer, you don't really need a streamer. 

If you have a dedicated 2 channel system that doesn't have a computer the streamer provides the functionality you get from the computer - internet connectivity to download/stream files, an interface to select music (often through your phone or tablet), and the firmware/hardware to decode the digital signal and send it to your preamp/amp.  It's basically another source, like a CD player, turntable, etc.

You may find that a dedicated streaming device provides better sound quality than your computer.
I gave up on hard media like vinyl and CD’s years ago and was an early adopter for computer audio. I only stream music through a dedicated streamer-dac box using a music subscription service. BTW, I uploaded my entire CD collection into a solid state drive that I plug into the streamer and access that music if I’m in the mood. So for me the convenience and very easy access to a broad music library is key for me. BTW, the sound quality is terrific IMO, with my gear. However, if you like CD and/or vinyl and the "work" it entails, that’s fine too.
This all clears up a lot for me.  Thanks, all!  Prob. For the foreseeable future, I’ll continue to stream tunes from my Mac > Airport Express....I’d eventually like to acquire a better DAC and go wired rather than wireless (rare dropouts but they do happen when the microwave oven is running!).  It all sounds pretty wonderful now, as is but...well...upgrade-itis lol.
I think the OP query has been answered, I’ll just chime in with reiterating that streamers and PC based streaming are essentially similar.  Streamers remove the PC from the equation, but are in themselves computers with specialized OS.  There are are many theoretical advantages to removing the PC and using dedicated audio components.  Having done both, they both can deliver great sound.  Personally, since I stare at a computer screen all day at work, I don’t wish to be dealing with one while relaxing with music at home, but ymmv 
I started with a NAD USB DAC streaming from my Asus laptop mainly HiRes files & Spotify. I also like the Jazz 88.3 from San Diego State University and a few other internet stations. Loved the quality but wanted more convenience since my wife loves music but is not at all technical.

Decided to upgrade to the NAD C368, but use a McCormack DNA 0.5 as my main amp. The Dac and Preamp are wonderful and with the bluos system I get what I want and she gets a simple to use streamer setup for her use. Now I can add other bluos  components to customise the house. Planning next to add a NAS storage to replace the 1Tb drive plugged into the back of streamer and some bluos speaks in a few places where I don't do critical listening but want enjoy some quality music separately from other current music on the main system.

So far, am loving the combination of quality sound and convenience.  BTW I added a Spotify family account so she could use her account while I use mine in other places including around the house and on the road.