In Texas hold'em, the last round of betting after the final community card is dealt. In stud, the third round of betting after each player has received their fifth card.
Make a strong hand.
Complete a full house.
In games where there are five community cards, the first three are dealt out and exposed together; this is called the flop.
In hold'em, the third round of betting, after the fourth community card is dealt. In seven-card stud, the second round of betting when a player is dealt their fourth card.
A draw to an inside straight, where only a card of one rank will make the straight, e.g. 6432, needing a 5 and only a 5.