3betting is an aggressive move in NLHE made by TAGs and LAGs pre-flop. 3betting quite literally means to make the 3rd raise in a pot; its main advantages include giving you initiative in the hand and keeping you on top of your opponent. Of course just like any other aggressive move 3betting is most profitable against tight-passive players. These player types rarely have enough gumption inside them to hit back at you, or call you in big pots, allowing you to make effortless steals all over the table.
For the record, a typical 3bet should be around 3x the opening raise. For example, in a .025/0.50 cash table: BB raises the pot $2.00 with 54 suited, CO then 3bets (re-raises) with AK to $6. BB Folds.
An optimal 3bet percentage is roughly 7%, in my experience this gives you enough call equity from your big hands such as AK because of your looser perceived 3bet range, whilst also preventing too many opponents seeing you as too wild or wreckless and challenging your 3bets. TAG players will only be 3betting their top 5% of hands, while the loosest opponents may 3bet up to 10% of their hands. Anything above this and you can just assume they’re a very bad player, I don’t see how anyone can profitably 3bet more than 10% of their dealt hands on a regular table without bleeding chips in the long run.
My regular 3betting range on a short-handed table includes 1010+ or AJ+. This is a typical TAG 3betting range, betting and fast-playing premium hands whilst only limping or flat calling non-premium hands such as suited connectors or face cards.
Loose-aggressive players tend to throw a lot more weight around and bully passive tables. They’ll commonly 3bet for value or to steal with 10Jo+, pocket pairs and suited connects/aces. Although they enter flops with a weaker range of hands – their merged 3bet range gives them greater EV post-flop. It’s extremely difficult to isolate or read into a LAG’s 3bet on the flop. For example, if a LAG 3bets pre-flop from MP and I call from BB with 66, on a flop like QK4, it’s incredibly difficult for me to play profitable.
The average player will be mostly be 3betting in position i.e. MP-LP. However, the problem with a polarised 3betting range is that it makes your style too predictable against regulars. Against better players you should commonly be looking to 3bet hands out of position (e.g. BB) because this gives you initiative in the hand and it offsets your positional disadvantage i.e. having to act first on each street. Bear in mind that poker is a game that commonly rewards aggressive play, you should never be too scared to 3bet a hand like 56 suited or broadways cards when deep stacked. These have a lot of flop equity for hitting decent mid-pairings and they also have excellent implied odds for hitting monsters.
Against fish, 3betting serves an added advantage of isolating the pot in heads up play. Although I’d normally not recommend 3betting with A10 or JQo, you can 3bet these hands for the sake of eliminating other players from the game. The EV comes from the opportunity to extract value from the fish in post-flop play.