I am playing poker in facebook apps and i feel that I am improving. And it's becoming addictive too LOL
Oh sorry bud - now I got you!
Buy-in is simply the cost to enter the tournament. Rebuy means you will have a second chance in case you bust out by paying the buy-in once again.
Regarding blind levels:
In a poker game, the two players to the left of the dealer have to pay blinds (small and big) - these are mandatory bets that need to be placed even before the cards are dealt. Small blind is half of the big blinds amount and the blinds count towards the first betting round. These blinds go up gradually and in our case - 12 minutes - the blinds will go up every 12 minutes.