Woo-hoo! A chance to go into lecture mode!
Draft is an 8-person tournament. Each of you starts with 3 booster packs in front of you. You open one, look over the 15 cards, and pick one. You then pass the remaining 14 cards to your left, and the person on your left passes you 14 cards. You pick one, and then pass the remaining 13 cards. By the time you’re done, you’ve picked 15 cards. Now you open a second booster pack and do it again, only you’re passing to the right. And then again with the last pack.
When you’re done, you have 45 cards. These 45 cards are yours to keep, win or lose. You’d get 45 cards if you just opened the 3 booster packs, but you got to choose your 45 cards out of a pool of 360, so there’s a pretty good chance they’ll work together well if you’ve selected wisely.
These 45 cards do not include resource cards, called “land” in Magic. You can add an unlimited number of those, of any color. According to Cryptozoic, you’ll also have an unlimited number of gems, if you happen to have cards with gem sockets. You’re building a deck of 40 cards or more. Since you’ll be adding 17-18 resource cards you’ll only use 22-23 of the cards you drafted. The smaller the deck, the better it usually plays, so you usually want to shoot for exactly 40 cards total.
Now you take your 40 card deck and play against other players, with their new 40 card decks.
Yes, and yes. One draft tournament is free, they pay for your entry fee and 3 booster packs. Like any Draft game, you keep the cards you drafted at minimum, plus any prize packs.
One common issue is that since you keep your drafted cards, it’s not unusual for people to take the Rare out of a pack even if it doesn’t fit their deck, just to have the single Rare you get in each booster, since they get to keep it. It depends on how tempting the rare is, and if one of the cards they’re passing up for the Rare is particularly good for their deck.