The poor girlfriend in a falty relationship who is actually a more involved booty call rather than a true girlfriend. The guy gets involved in the relationship so that when he is with her he has a more guarenteed chance to have sex. He will shower her with gifts, sweet talk her on the phone, and celebrate random anniversaries. This is also the boyfriend who will not put his relationship on a social networking site and makes up some excuse when his real reason is he could tell a random girl that he doesn't have a girlfriend. This is most common in college. As mentioned before he feels that this is perfect for the random breaks, he knows that he will have sex when he is home.
Jill is just some guaranteed ass, I take her out for her birthday, get her some flowers than I get sex whenever I want.