The term freeroll is also used to describe a tournament with no entry fee but the use of the terms 'free' and 'no entry fee' can be misleading because some freerolls require a payment at some point to gain entry to the tournament.
The prize pool, instead of being an accumulation of the entry fees minus a fee for the 'house' (the way pay-to-play tournaments are typically constructed), is derived from a donation from the house, sponsorship fees, admission charged to spectators, broadcast rights fees, or any combination of these. Sometimes a particular cardroom or casino (either traditional or online) will offer a freeroll tournament to frequent players. Invitation-only tournaments are frequently freerolls.
PartyPoker is one poker room that offers 'freeroll' tournaments and games for players, with entrants not being charged for poker tournament entry.
The opposite of a multi-table tournament is a single-table tournament, often abbreviated STT. A number of places (typically, nine or ten) are allocated at a single table, and as soon as the required number of players has appeared, chips are distributed and the game starts. This method of starting single-table tournaments has caused them to be referred to as sit-and-go (SNG) tournaments, because when the required number of players "sit," the tournament "goes." Sit-and-go tournaments of more than one table are becoming more common, however, especially in Internet poker. A single-table tournament effectively behaves the same as the final table of a multi-table tournament, except that the players all begin with the same number of chips, and the betting structure starts much lower than would likely be the case at a MTT final table. Almost invariably, fixed payoffs are used.