There are quite a few manufacturers which offer (or have offered) a great many tubesets in varying alloys. The best known are Columbus and Reynolds, but there are quite a few more with Falck, Dedacciai, Oria, Mannesmann, Poppe & Pothoff (Stainless), Tange, Ishiwata, Vitus and True Temper etc. Usually you will find a sticker explaining what you have spent your money on, usually with a fancy name and sometimes the specification. Most manufacturers start with a tubeset from 25cromo4 with a 0.8 mm straight wall, followed by several series in butted 25cromo4, some higher end versions with modyfied cromo (up 20 %) and some high-end version of such strenght that the wallthickness can be reduced to 0.4 mm.
If the sticker says 25cromo4, it will decribe a steel tube (the 95% Iron content is so obvious it doesn't need mentioning) 2.5 % carbon (again carbon is always used, so we will leave out the C) 4/4=1% chromium and some molybdenum. But the alloying elements sound wonderfull (I love Oakley with Plutonite and (where did they get this) Unobtanium) so copywriters will make the most of it and then some.Titanium is used in stainless steels to improve the weldability, but ad-writers will let you believe that you're getting a Ti frame. I'm waiting for the day 'they' discover it is also an important ingredient in white paint!