How Tourneys Work:

There is an initial fee, a casino charge, and then buy-ins and add ons.  
these are all slightly different.
Initially you pay the casino charge to get you into the tourney, and then 
the required initial fee that will get you chips.  Everyone gets the same 
amount (X) of chips.  
A re-buy is a point in the game where you pay cash to purchase the same 
number of chips you started with.  The amount to do this is usually the 
same as the initial fee, without the casino charge.  The re-buys are 
limited in one of a few ways:

1.  You can re-buy unlimitedly (in the first R rounds) if you have 
less than the initial X number of chips.  that means, 
obiously, you can't rebuy many times at once, and you can't rebuy if 
you're up, or even if you're down less than X and have already rebought.
2.  There are a limited number of rebuys overall (usually 1).  this means 
you can probably do it without limitations on your stack, but you can 
only do it once.  once you lose your chips, you're gonne.

Anyway, the tourney goes on its merry way for a little while.  Every 
certain amount of time (someone said 20 minutes, for instance) the blinds 
go up (thus you ante-equivalent more).  This is a round (I'm pretty sure, 
anyway).  After a few rounds (usually half of them, or 3),
there is a break.  After this point, the rebuy situation changes.  
Usually, you can't rebuy at all.  After the break, however, you can 
purchase an Add-on (initial fee) regardless of how many re-buys you've 
made or how many chips you have in front of you.  This varies by tourney.
The blinds then go up substantially every 15 minutes.  

The tourney works like this:  There are N contestants.  Once a contestant 
is out of chips (all-in and loses) he is eliminated.
Contestants get eliminated, tables are joined together. It is _not_ the
"winner advances" mentality you might have seen in movies.  Eventually, 
all remaining contestants are on the same table.
Prizes go to the first 8-10 finishers, usually.  ALL of the take-in (entry, 
rebuy, add-on, etc...everything but the casino fee) for every player is 
awarded as prize money (usually).  A normal breakdown could be 40% to 1st 
and 1% to 10th, with odd amounts in between.