Pocket cards Each player gets the first two cards dealt face down. These card are often referred to as the pocket cards.
The flop The first three cards (the community cards) which are simultaneously dealt face up and shared by all players.
The turn, or 4th Street The fourth community card.
The River The fifth and final community card which is dealt alone and is similarly available to all players, river metaphors are legion. "Going to the river" indicates you've stayed in until the bitter end, while "drowning in the river" suggests that it might not have been such a good idea.
Bad beat When you go to the river with an appalling hand and draw the one card that you need to win the pot, it's a bad beat. You might win the money but you'll win no friends with this class of play.
Short stack Not something you want. When you have fewer chips than everyone else you're playing on a short stack.
All-in When you throw all your chips into the pot during a single hand it tells the table you either have a monster of a hand which you're certain to win or you're so short-stacked that you have nothing to lose so you may as well gamble the lot and go home to bed. Alternatively, you might have a hand of muck and want people to think you have a monster hand.
The nuts The best possible hand in a given deal. With this, going all in is often a good idea.
Tells The little ticks everyone has which tell your opponents you have the nuts. Good players will be able to tell from the merest twitch of your eyebrow and fold accordingly.