A bag is an extra trick, above the team's bid.
For example, if your team's bid totals to 2, and you actually take 5 tricks, then you've picked up 3 bags.
To cover is to play a card that is higher in rank than the current card that will take the trick, too keep a player from taking a trick. Usually people use the term when a player has bid nil.
For example, North has bid nil. East plays the 3 of clubs and North's lowest card is the 5 of clubs, so he plays that. West plays the 2 of clubs. South plays the 7 of clubs to cover North.
To duck is to play a card that is lower in rank than the current card that will take the trick.
For example, if West leads the trick with a 3 of clubs, and you play your 2 of clubs when you have a higher club card, you are ducking to avoid taking the trick.
The person who plays the first card in a trick is said to lead the trick.
You are long in a suit if you have more cards of that suit than average.
For example, if you have 7 diamond cards, you are long in diamonds. Some people might say you are long in a suit if you have even 4 cards in that suit, but it's more common to use the term "long" with more than 6 cards in a suit.
When a team accumulates 10 bags, they roll, and 100 points are deducted from their score.
For example, suppose your team had a score of 199, with 9 bags. They bid a total of 3, and took a total of 4 tricks during the hand. Since they made their bid, they get 30 points. They also get one extra point for the bag that they took. The math is: 199 + 30 (bid) + 1 (bags) = 230. The one extra bag gives them 10 total bags, so they roll. Subtract 100 points for the roll to get 130, their score at the end of the hand. Their bags are cleared in the roll, so they now have 0 bags.
Here's a more complicated example. Suppose your team had a score of 259, with 9 bags. They bid a total of 5, and took a total of 8 tricks. Then they'd end the hand with 2 bags and a score of 212. The math goes like this: 259 + 50 (bid) + 3 (bags) = 312. Subtract 100 points for the roll to get 212. One of the bags was absorbed during the roll; they are left with 2 bags.
When a team is set, it means they did not make their bid. To set an opponent is to keep them from making their bid.
For example, if your opponents bid a total of 6, and they only take 5 tricks, then they've been set.
You are short in a suit if you have less cards of that suit than average.
For example, if you have 1 or 2 club cards, you are short in clubs.
A trick is the pile of 4 cards that is collected by the person who placed the highest card in the pile.
It is also sometimes used to mean a discrete phase in the game of Spades, during which each of the 4 players plays one card.
A hand is void in a suit if it contains no cards of that suit.