Attaching -동안 to a length of time indicates duration, or during that time. If you attach it to a verb, then you are saying while that action was happening.
length of time + 동안
1. Attaching 동안 to a length of time indicates during that time.
한국어를 얼마나동안 배웠어요? – How long have you been learning Korean?
일년동안 두번 가요 – I go twice a year.
이개월동안 한번 가요 – I go once every two months.
AV + 는 + 동안(에)
2. Attaching 는 동안 to an action verb indicates while that action was happening.
내가 자는 동안에 눈이 많이 내렸어요 – While I was sleeping, a lot of snow fell.
You can find more frequency words in this article.