What does the number on chainsaw chain mean?

the two big names in chain saws is stihl and husquarna. chainsaws comes in three general uses. 1: hobby/ household use. light use 2: farmer. medium use 3: professional heavy use that in turns, means how much you will use your saw, and what "power" you are looking for. the numbers on the older saws, were really simple, it was the cc displacement of the cylinder. examble: 026 stihl = 26 cc, well all most 26 cc. 036 sthil= ????? yes 36 cc, well all-most and so on with stihl. its a matter of size with stihl, then you have the letter coding on them as well, like the new t200 (old version 020) t = trimming, 200=020. it is a small professional climbing saw, you use for trimming trees while climbing. all major brand names in the saw world have changed the numbers and letters on their products so many times, that even the every day user has to look it all up on line. if you want to now about the numbers on the bar let me know