Trips
Three of a kind using one hole card and a pair on the board. Like a set, but easier for others to read.
You call from the cutoff with K9 and the flop comes 9-9-4. Trip nines, King kicker — one hole card plus the pair on the board. Same three of a kind you'd make holding pocket nines with one landing on the flop, but the difference matters. With pocket nines your two matching cards stay hidden until showdown, so the hand looks like nothing to anyone watching the betting. With a 9-9 flop, the whole table sees the pair, and everyone still in knows trips are possible.
That visibility cuts both ways. A paired board slows opponents down — they know trips or better are out there — so you can get value from hands that would fold on a dry, unpaired flop. It also lets them play back at you, because they know you know. A check-raise on a paired board carries more weight than one on an unpaired flop. Kicker matters more here too: the three of a kind is shared with the board, so two players can both hold a nine, and the side card decides it.
The common mistake is betting trips like a monster no matter the board. A paired board is exactly where someone has quietly made a full house or holds a bigger kicker. Beginners barrel in without stopping to ask who else could have a nine.