this is what happens:
Two single people have met, often through mutual friends. They get acquainted. A date is suggested; this could be on the day of meeting or some time afterward. Due to the fact that the two people are experienced with relationships the suggestion of a date is mutually agreed. They go on the date. Unless one of the two finds something disagreeable, they have sex. This continues for a few more dates. If things are running smoothly, they move in together.