There are three kinds of sex in a marriage.
The first is Kitchen Sex. This is at the beginning of the marriage; you'll have sex anywhere, anytime. Hence, in the kitchen.
The second kind is Bedroom Sex. You've calmed down a bit, perhaps have kids, you gotta do it in the bedroom.
The third kind is Hallway Sex. This is where you pass each other in the hallway and say, "Fuck you."
There is also a fourth kind of sex: Courtroom Sex. This is when you get divorced and your wife fucks you in front of everyone in court.