Used to apply to a certain betting structure in poker games. The typical definition of a structured hold'em game is a fixed amount for bets and raises before the flop and on the flop, and then twice that amount on the turn and river. Example: a $2-$4 structured hold'em game: bets and raises of $2 before the flop and on the flop; $4 bets and raises on the turn and river.
The individual rules for a game, specifically the betting trends.
The limits put on the blinds/ante, bets, and raises in any particular game.