An optional extra blind, usually posted by the player to the left of the big blind, which typically gives that player the right to last action before the flop.
Straddles promote action because they seed the pot with additional chips before the start of the deal. This tends to lead to wilder action and larger pots. Allowing them can improve the quality, strength and viability of weak or boring poker games
, which is why many casinos
allow them. The downside is that they can slow the game down, and sometimes create too much action for certain players, putting undue pressure on risk adverse or low bankrolled players.