VPIP
VPIP (Voluntarily Put $ In Pot) is a stat showing how often a player chooses to put chips in preflop by calling or raising, instead of folding.
VPIP stands for "Voluntarily Put money In Pot." It's a percentage that tracks how often a player puts chips in the pot before the flop by their own choice, meaning they called or raised rather than folded. Posting the small or big blind doesn't count, because that money is forced, not a real decision. A VPIP of 25 percent means a player voluntarily enters the pot in about one out of every four hands dealt to them.
You'll mostly see VPIP come up when people talk about how loose or tight someone plays. It's one of the first numbers tracking tools show next to a player's name, and it pairs with a sibling stat called PFR (preflop raise percentage). A low VPIP means a player folds a lot and only enters with strong hands; a high VPIP means they get involved in many pots, including weaker ones.
As a rough guide for full-ring tables, a VPIP somewhere in the high teens to low twenties is fairly solid and selective. Much higher than that and a player is probably entering too many marginal hands and bleeding chips over time; much lower and they may be too predictable. For beginners, the simple lesson is that folding more of your weak starting hands keeps your VPIP healthy, and tighter is usually safer while you're learning.
Example
If you're dealt 20 hands and you call or raise preflop in 5 of them (folding the other 15), your VPIP for that stretch is 25 percent. Limping in with 7-2 offsuit from under the gun is a voluntary action, so it would raise your VPIP, while folding it keeps you tighter. Note that checking your option for free in the big blind doesn't count, since you didn't choose to add chips.