10 0 or 10 u; 5 2 - meaning

I can't work out what the numbers/ signs after the time indication means.

the first number is minutes, the second is seconds added to your clock after you make your move. so 10/0 means 10 minutes for all your moves. 10/10 means ten minutes for all your moves PLUS 10 seconds is added every time you move. 5/2 , in the same way, means five minutes plus 2 seconds per move for each player. 

so x/y means x minutes per player, plus y seconds added to each player's clock every time that player moves. 

common time controls on chess.com are, for example, 15/10 meaning 15 minutes plus an extra 10 seconds per move for each side. I don't know anything about blitz time controls, but it would be the same thing. If there is a common blitz time control, say, of 1/5, that means each player gets 1 minute for all of their moves PLUS they get an additional Five seocnds added to their clock every time they move. 

"Increment" means 'time added to your clock every time you move'. Hope this helps. 

And "u" stands for "unrated".

Great, thanks guys.

ahhh, I didn't answer what 'u' meant, because I didn't know, cuz I rarely play unrated. thanks