The "buyin" is what each player pays to enter the tournament. If the
buyin is play money, that means you use a certain number of play money
credits to sign up. If you win the tournament, you'll win play money
credits in return.
A "freeroll" tournament is one that does not require a real money buyin
but pays out a prize pool of real money. These are a fun way for a
beginner to start because there's no risk of losing any money but a
chance to win some in return. There are a few kinds of freerolls. The
best kind is absolutely free: you just sign up. Not all sites offer
these. The more common kind is a "frequent player point" (FPP) freeroll.
You use points earned in the poker site's loyalty program to buy in.
These are very popular. At some sites you can even earn FPPs by playing
in the play money games, so this can be another good way to get started
without going to the trouble of depositing real money.
A real money buyin means you use real money that you have deposited in
your account to buy in. We talk about real money isues in a
later section.