(I see Cyberhwk already answered, but I typed this so I’m gonna post it anyway.)
SNG - sit-n-go, a tournament that doesn’t have a scheduled start time. It starts as soon as the required number of people sign up. For a single-table SNG, as soon as ten players sign up, it starts.
NL - no-limit, where you can bet all your chips at any time. (Compared to pot-limit, where the maximum bet or raise is the amount that’s already in the pot.)
monster raise - a large bet, which usually indicates a very strong hand. You’ll have to risk a lot of your own chips to call; you only do that if you have a very good hand or know the other player is bluffing.
nine high - a very weak hand. The order of poker hands goes straight-flush, four-of-a-kind,… two-pair, pair, high card. (At the showdown, if nobody even has a pair, the higher card wins.) In hold-em, you have two cards of your own, and five shared cards face up, so you’ll sometimes leave the shared cards out when describing your hand. (If there’s an ace and king on the table, both players will have ace-high. The cards in your hands will be the tiebreaker; my nine-high beats your eight-high.)
call on the river - Hold-em has mutliple rounds of betting in each hand. The down cards are dealt, and everybody bets (or folds). The first three shared cards are dealt (the flop), and another round of betting. The fourth card is called the turn, and another round of betting. Then the last card, the river, is dealt. Another round of betting, and if the wager is called, the cards are turned face up and the best hand wins the pot. For the first three betting rounds, you’re (usually) playing the percentages. If I’m holding two hearts, and there are two hearts on the flop, that’s probably not much of a hand. But I’ve got two chances, the turn and the river, to get a fifth heart and then I’ve got a flush. But after the river, the element of chance is gone. Each player has their final hand. There’s no more chance that another player might get a lucky card to make a winning hand.