The word while has a few related meanings:

1. A period of time, usually short. When someone says “wait a while,” they mean wait for some time, though probably not too long. You might read for a while after dinner, or visit a friend you haven't seen in a while. The phrase once in a while means occasionally, like “I eat ice cream once in a while, but not every day.”
2. At the same time as something else is happening. You might listen to music while you do homework, or think about soccer strategies while walking to school. This meaning connects two things happening simultaneously: “While the rain poured outside, we stayed cozy indoors.”
3. Even though, or despite the fact that. Here, while introduces a contrast: “While I enjoyed the book, I thought the ending was weak.” This usage shows that two different or opposite things can both be true. You're acknowledging one fact (you enjoyed it) while adding another that goes in a different direction (the ending disappointed you).