How to read tubes?

Where I can get the information on how to recognize parameters on tubes just by only reading it's names
12AX7, 6692, 3550, 6SN...???

Can someone provide an example?
Why some tubes have only numeric name and some of them alpha-numeric.
The different names, numbers only have to do with the country of origin, or whether they are military or consumer tubes. For example: 6SN7, VT231, and 5692 tubes can all be used for the same applications. Some of the lettering on some tubes has to do with maximum voltage and wattage. Again for example the 6SN7:

5692 - 275 Volts maximum & maximum 1.75 Watts per section
6SN7GT/WGT -- 300 Volts maximum & maximum 3.5 Watts per section
6SN7GTA/GTB - 450 Volts maximum & maximum 5.0 Watts per section
If you used a 5692 tube where you really needed a GTA, it would run hotter and not last nearly as long. (Assuming it does not blow out quickly). A GTB used in a lower voltage situation would work perfectly fine and would last a long long time since it would run cooler. The GTA/B I think were designed for the higher voltage needs of televsions, etc.

There is some information on tube basics, matching, biasing, etc, and what types are similar, etc (like above) at

Small signal tubes such as 12AX7 and 6DJ8 are usually coded so that the first number is the heater voltage, ie. 12V or 6V. In many instances, four numbers indicates that the tube is designed for industrial and/or military use such as 6922. Tubes that begin with a letter are often European tube types, E88CC being an example. The best source on tube parameters is the "RCA Receiving Tube Manual" which was published annually for many years. It gives the operating parameters of all commonly available domestic tubes along with great theory and implementation. If you read the book thoroughly you will a have greater understanding than most of the self-professed tube experts. If you also get a good tube substitution manual such as Sam's you will be able to determine the equivilent industrial and European tubes. Good luck, the quest starts here.
Viridian gives good advice. You cannot recognize tube parameters just by reading names because the info is not in the names. Here are a few online links that explain what the “operating parameters”, as Viridian calls them, are.

An online copy of an RCA tube manual (as mentioned by Viridian) that talks about the general measurements that determine how a tube performs. RCA Manual

The discussion about tube characteristics starts at page 10. Tube curves and load lines are about the most useful general info you can get about tubes and tube circuits.

There is also a discussion of how to use plate curves and tube load lines here. This is a classic article by Norman Crowhurst.

A short description of what a tube tester does is below. It gives you specific info about the tubes in hand that cannot be obtained from general info above. Rozenblit's site

If you want to buy a book Bruce Rozenblit’s book “Beginner’s Guide to Tube Circuit Design” describes all of this very well and is only about $25.

Clueless, thanks so much for sharing the excellent links; the Crowhurst article is particularly interesting.