Definition of MTT
An MTT is a Muti-Table-Tournament, in short, a multi-table tournament. Multi-table tournaments are different from sit'n'gos which are a form of tournament poker, but on a smaller scale. A multi-table tournament starts at a fixed time, has a fixed entry fee and an unlimited number of entries. It is a very popular form of poker, especially in casinos. Since the explosion of poker in 2003, countless new tournament variations have appeared. The rebuy tournament, re-entry, KO, Bounty, turbo, hyper-turbo, shootout, etc. The list goes on and on!
MTT vs cash games
If you want to get into online poker, this is probably a question you'll ask yourself; do you want to focus on tournaments or cash games? MTT's can be spread out over several days, even online. If you are playing big online tournaments, you could be in Day 1 which will stretch over 10 hours in the day and if you are still in the tournament after those 10 hours, you will come back for Day 2. In tournament play, there is more variance, a lower caliber of player and a chance to win big. In cash games, there is less variance, the games start and end when you want them to, but the profits are more gradual. It's up to you to decide what you like!