When do I use "during" and when do I use "while"?

Use "during" before a noun (a person, place, thing, or event).

During the movie, I fell asleep. (movie is a noun)

Use "while" before a verb phrase or a subject + verb (an action).

While I was watching the movie, I fell asleep. (was watching is an action)

This is the short answer; more explanation could be given.