Three cards for a straight flush with two inside gaps, e.g. 965 of clubs.
A side bet on a winning hand. The player must draw a higher card than the one shown to win.
The best strategy of keeping or discarding cards to maximize a player's long-term winnings (not each hand in isolation). This varies from game to game.
In video poker, four cards of the same suit.
Four cards almost in sequence, with just one gap, e.g. 9765.
Four cards of the same suit almost in sequence, with a gap of one, e.g. KQJ9 of hearts.
Four cards of a royal flush, needing one and only one card to complete the hand.
Four cards that can potentially make a straight, either inside (e.g. J1087) or open ended (e.g. J1098).