Ante
A small forced bet posted by every player before the hand starts, on top of the blinds, adding dead money to the pot regardless of who wins it.
Antes matter most in the tournament endgame, where they can dwarf the blinds as stacks shrink. More dead money in the pot makes a successful shove worth more, and makes calling a shove more likely to clear its price, so both the jamming range and the calling range widen as antes increase relative to the blinds.