Hi, hvard92
I'll start w/ the easy question.
In cash games rake is a fee that is taken from each pot.
It is usually stated as a percentage, and the percentage may vary depending on the limit you are playing. In addition, there is a limit (called a cap) to the amount of rake.
For example, if the rake is 5% with a limit of 1$, then if the pot is $1 then the rake is 5 cents. If the pot is $10, then the rake is 50 cents. If the pot is $20, then the rake is $1, but no matter how big the pot is after that, the rake will always be $1.
The rake is taken from the pot before it goes to the winner(s), however ever player in the hand at the flop is credited with a share in the rake in proportion to how much they contribute to the pot. This credit determines how many loyalty points a player earns for that hand.
In most cases, players who fold before the flop are not credited in any part of the rake in the pot unless they put money in before they folded.
Rakeback occurs in various forms.
Some rooms grant loyalty points that can be exchanged for cash, for bonuses or tournament tickets.
Some rooms have schemes in conjunction with affiliates like PokerStrategy.com that actually pay back a percentage of the rake.
Each room will have somewhere on there website a table of rake charged.
For tournaments, the buy-in is usually written as $X.XX + $Y.YY where the $X.XX goes into the prize pool and the $Y.YY portion is a fee which earns you points, or is subject to rakeback. Note that in tournaments, no rake is charge hand-by-hand.
I probably left stuff out, but the others will fill it in.
Cheers,
--VS