Blinds
Forced bets posted by the two players to the left of the dealer button before any cards are dealt.
The small blind is usually half the size of the big blind. Blinds make sure there is money in every pot, which gives players a reason to compete. Without them, everyone could wait for Aces.
Blinds move one seat clockwise each hand with the button. In tournaments they also increase on a schedule, which forces action as the event goes on.
Example
A "$1/$2 game" means the small blind is $1 and the big blind is $2.