While describes a length of time. If you were describing a first date, you might say, "We sat there for a while in an incredibly awkward silence."
Use the word while to talk about an unspecific period of time, like when you ask your friend if you can borrow his notebook for a while. While is also a conjunction that describes things that happen at the same time, like crying while watching a very sad movie. The Old English root of while, hwil, is interesting because the w and the h are switched, but the meaning is the same: a space of time.