Blackjack is normally played against the house. In fact, this is one of the aspects of casino games that make them different from poker. At the Texas hold'em tables, you're competing against the other players.
Blackjack tournaments combine the competition with other players that poker offers with the game rules and features of the card game 21. Various formats, rules, and prize structures are found online and off. But they all feature that competition between players that make tournaments so interesting.
Most tournaments require a buy-in of some kind. Like poker tournaments, blackjack tournaments use the buy-ins to fund the prize pool. But some tourneys are free to enter—these are called freerolls. Casinos use these free blackjack tournaments as a marketing tool to draw people into their establishment in order to get them to gamble real money on their other games.
If you pay real money to play in a tournament, it stands to reason that the cash payouts will be larger. These payouts are a function of the number of players, the entry fees, and the percentage of players who are getting payouts.
Here's an example:
You're playing in a tournament with 99 other players. Everyone pays $110 to participate. The prize pool is $10,000. (There was $11,000 in entry money, but the casino kept $1000 in order to pay for their effforts.)
First prize pays $5000, 2nd prize is $3500, and 3rd prize is $1500. The other 97 players get nothing.
Most tournaments offer a larger prize distribution than that, but the example was meant to illustrate how it works in a general way.
When you "buy in" to your event, you get a set number of chips. These have no actual monetary value. They're just how you keep score during the event. Everyone starts with the same number of chips.
When you lose all your chips, you're busted out of the tournament. An exception is a re-buy tournament, where you can buy back in. Usually they limit re-buys to the first few rounds. Past a certain point, you're not longer allowed to buy back in.
Tournaments are organized into rounds or levels. In some tournaments, your stack is whatever you build it up to throughout the event. In other tournaments, you get a new stack every level. Rules vary.
Your strategy can and should change based on how the levels and chips are handled. You might need to play aggressively if you're behind. You might need to play more conservatively if you're way ahead. And it might not matter much if you're getting a new stack of chips on the next level.
You can find all kinds of events available. Here are some of them:
Scheduled Tournaments – These have a set starting time and a set ending time. You have to pay your entry fee in advance to participate. You also need to show up on time for the event. The size of your chip stack at the ending time determines how well you've placed compared to your competitors.
Sit and Go Tournaments – These tournaments are usually smaller and start as soon as a set number of players have signed up and paid their entry fees. Sometimes these events have as few as 9 or 10 players. The format is largely based on the format of the same name that became popular during the online poker book.
Satellite Tournaments – These are tournaments that, instead of offering a cash payout, provide the winners with entries into bigger tournaments. These are also sometimes called "qualifiers" or "qualifier events". I like these, because they give me a chance to play for a large prize I wouldn't normally be able to afford to compete for.
Guaranteed Tournaments – These are tournaments which offer a prize pool of a certain amount regardless of how few entrants there are. If you can find a guaranteed tournament that doesn't have as many players as the casino anticipated, you can put yourself in an overlay situation. This means you have more equity in the prize pool than your entry fee would indicate, because there are fewer players than warranted.
Here's an example:
A casino has a $10,000 guaranteed blackjack tournament. They're anticipating $100 per player with 100 players signing up. Each player has, assuming they're all equally skilled, a 1/100 chance of being the winner.
But if only 50 players signed up, each player would have a 1/50 chance of winning. But the prize pool would still be just as large.
THAT is an overlay. It's a positive expectation situation. The more situations like this that you can put yourself in, the more money you can expect to win gambling.
If you're at all familiar with blackjack, you know that it's customary for casinos to vary how many decks are in use, when you can double down, and when you can split. They often have different rules about surrendering and whether or not the dealer hits a soft 17.
All of these rules are fair games for changes during a tournament, too.
But tournaments also have rules that govern how the tournament is run, too. For example, in an elimination tournament, the players with the lowest chip stacks are periodically eliminated from the competition.
The tournament style is a fun and exciting way of enjoying blackjack that pits you against the other players at the table. If you can find a tournament where you can play for free or with a low buy-in, you can get a lot more time at the table than you usually would. And if you can find an overlay situation, you can make a tournament into a positive expectation gambling event for yourself.
Your best bet is to get familiar with the rules variations beforehand so you'll know the best strategy to employ when you play.