don't know what happened... I thought you disconected. It must have been a problem with my wi-fi.
UU and BL are pokémon categories.
In each category you can use some pokémon.
Ubers are the most powerful, OU (often used) are great ones, BL (border line) are good, but not as much as OU so they can be used in OU and UU (UU means under used or unusually used) and the last category is NU (never used).
If someone says he wants to play UU, it means there will be allowed pokémon from BL, UU and NU.
You can check in which category is a pokémon here
http://www.smogon.com/dp/pokemon/
Don't worry about it, everybody makes mistakes ;)