What are fuses used for?


I have, I’m sure to many, a very dumb question. I keep reading about fuses.  I have a fairly sophisticated system and have never come across the need for a fuse.
Can someone tell me where these fuses go and what they’re used for?
128x128rvpiano
Some crafty manufacturers found that by claiming a lot of nonsense about Special fuses made with beeswax or silly pseudo science, with very little rational explanation of why they could make this magic: "New UEF Graphene coating, two years in development, and UEF quantum treatments make the BLUE fuse significantly more holographic and dynamic than even the incredible SR BLACK fuse. Resolution and musicality are second to none"...like that...would make some easy tweak bucks...that’s pretty much it. If 40,000 hopeful and faithful bought in, as says Kaitty, that’s just sad and likely inaccurate, but far more than 40,000 HAVEN’T bought in (they perhaps haven’t heard about the astonishing benefits of fuse "upgrades"). For weird reasons better explained by non-layabouts, Conference Call Kaitty has issues with the fact that I actually did a pretty thorough test, and am a successful (admittedly frequently overpaid) live concert sound engineer...likely more fun than being an imagined Audio Insider.
Wolf, we all know acoustic engineering school is a scam. They don’t teach anything to prepare you for high end audio. They don’t even teach engineering. Give me a break. They teach you how to be a knob turner and wire puller. Though, on the plus side, being all thumbs might actually be good for knob turning. You should run down with great haste to whatever two-year podunk school you went to and demand your money back. No offense.
No offense taken there Kaitty as my skills come from over 5 decades of on the job experience as a working musician with no time for whatever Acoustic Engineering School might offer. My experience of working with those having been "trained" varies from smart and talented people to those with zero aptitude or talent. Ya never know. I get these live sound gigs from reputation only...sorry Kaitty...I know this bothers you, and my interest in audio has also been due to many years of practical experience, although it's only been during the last 30 years or so that I've been able to afford the gear I want, and focus on hifi instead of the musician gear needed to play live constantly as well as do personal and commercial recording work. As an aside...in the fourth grade I was trained by somebody in the audio-video department of my elementary school to run the 16 millimeter projector for a teacher with severe "projector phobia"...they'd take me out of my class from time to time and off I'd go to wheel a projector set into her classroom, which I thought was GREAT. That's where that stuff started I suppose.
What I glean from your post is that fourth grade was a watershed year in your development. 👦
@ geoffkait1

I worked with several Acoustical Engineers (some PhDs) in the past, their coursework all expanded on Mechanical Engineering as this is how acoustics is best modeled. Just a plain old BSEE here.