what's the difference between bullet and blitz, and ect?

Basically 1-2 is bullet 3-14 is blitz and 15+ is rapid.

That's the time control in minutes, and is the initial time allocated - there's also the increment (the amount of time added after every move you make) that doesn't affect the category but does affect the game play quote a lot - so both 2|0 (2 minutes to start, no added time) and 2|1 (2 minutes to start, 1 additional second for every move you make) are classed as bullet games, but the latter can play more like a 3|0 blitz game than a genuine bullet game.

There are also hyper bullet time controls where you start off with less than 1 minute - results of those games are currently part of your bullet rating calculation, but the development team are looking at that.

Yeah, anything faster than 1+0 should not count for bullet.