The first is Smurf Sex. This happens during the honeymoon period; you both keep doing it until you're blue in the face.
The second is Kitchen Sex. This is at the beginning of the marriage; you'll have sex anywhere, anytime, even in the kitchen.
The third kind is Bedroom Sex. You've calmed down a bit, perhaps have kids, so you gotta do it in the bedroom.
The fourth kind is Hallway Sex. This is the phase in which you pass each other in the hallway and say, "Screw you!"
There is also a fifth kind of sex: Courtroom Sex. This is when you get divorced and your wife screws you in front of everyone in the courtroom.