a sit and go tourney is a tournament that begins when all of its places has been filled, rather than at a specific time. sit and go(SNG) tourneys are generally one table affairs(usually 9 or 10 players paying out to the top three).
A satellite is a tourney where the winners/people who cash get entered into another bigger tournament. Say there's a $2 satellite tournament, and the winners get entry into a $10 tournament. For every five $2 entries there will be one winner to the next tournament.
mtt=multi-table tournament, as opposed to a single table tournament, so yes, any tourney over one table is a mtt.
hold em mixed? er, pass, don't remember that expression.
btw, Ive just worked a nightshift, so my brain isnt working brilliantly right now, feel free, anyone to correct me on the above...........