Velvet RiverBig Blind
The larger forced bet, posted by the second player to the left of the button. It sets the minimum bet for the hand.
The big blind acts last preflop. If nobody raises, the big blind can check and see the flop for free. Players measure stacks and win rates in big blinds: "100 big blinds deep" or "winning 5 bb per 100 hands".
Example
With $2 already in the pot, the big blind can defend a raise to $6 by calling only $4 more.