IMO, tourneys are a lot more fun than ring games. There is a clear beginning and end and you can easily measure how well you did vs. the competition. Its more dynamic, in that strategy changes based on the blinds, number of opponents and where you are in the money. That said, in general, I think ring play is more profitable, though not for everyone.
3 basic types of tourneys:
MTT: multi table tourney - These are the large fields of 100s or 1000s of players.
STT: single table tournament - 9 players, 1 table.
Multi Table SnG: 18-45 players, 2-5 tables.
Pokerstars also has a 180 player SnG, but I would classify it as a MTT.
Cost to enter tourneys is in 2 parts (e.g. $3 + .40). The first is the buy in. This money is divded amoung the winners. STT: $3 x 9 = $27 prize pool. The second amount is the fee that goes to
pokerstars. That's how they make their money for hosting.
Stars has a lot of good tourneys for beginners. MTTs can be a low as .10, $1, $2, $3 buy ins. STTs are as low as $3 or $6. The 180 MTT/SnG is $4. Stars also offers 18 and 45 person SnGs for $1 or $1.50.
A "Turbo" is a tournament in which the blinds increase more rapidly than a regular tourney.