In order to play online poker tournaments for real money, no matter if it is multi table tournament or Sit & Go they have to make a buy-in which includes service fee. For example, if you want to participate in a multi table tournament with a $50+$3 buy-in, $50 you pay to receive starting stack (and also that money go towards the prize pool) and $3 is the service fee taken by the online poker room. Such service fee is called tournament fee.

Unlike the limited amount of take that can be taken by an online poker room, the service has no maximum limit and it will always be anything from 6 to 10% of the part of tournament fee that goes to the prize pool.
Sit & Go (often mentioned as SNG, S&G and Sit’n'Go) online poker tournaments are the tournaments that don’t have scheduled starting time. Sit & Go tournament begins whenever all of the available seats are taken whether it is 6, 9, 18, 27 or 48 seats. Generally speaking, there may be any number of participants in Sit & Go poker tournaments, but as a rule they have a number of player seats that we mentioned above. Additionally Sit & Go tournaments may come in turbo, super turbo and matrix modes and can be a sattelite tournaments for the bigger ones or straight cash tournaments.