Board texture
How connected and suited the community cards are. Wet boards hit ranges hard; dry boards miss them.
You raise UTG with A-Q and the button calls. Flop comes 9-8-7 with two hearts. About as wet as it gets. A ten or a six gives an open-ended straight draw, two hearts give a flush draw, and hands like T-6, 6-5, or 9-8 already have a made straight or two pair. Your ace-high has two overcards and little else, a coinflip at best against what called. Compare K-7-2 rainbow: a dry board where nothing connects, no flush draw exists, and the only hands to worry about are a king or a set.
Texture decides how hard you can bet and how often you can bluff. On K-7-2, a continuation bet works almost every time — the caller's range rarely improved, so you can fire with air and take it down. On 9-8-7 with a flush draw, the bet has to beat real equity: draws that will often get there, and made hands that already beat top pair. Texture tells you whether the caller's whole range got stronger or stayed put, apart from your own two cards.
The common mistake is betting on autopilot — same size, same frequency, wet board or dry. That bleeds money on wet boards, where opponents have the hands and draws to call with, and leaves money behind on dry ones, where you could bet bigger and more often because nothing back there wants to play.