"I watch the movie at a theatre"
Translation:나는 극장에서 영화를 봅니다
Someone answered this on another question. So basically 저 is used to lower yourself and -ㅂ니다 is used to raised the listener. If you're higher than the listener, you can raise the listener without lowering yourself, like in this sentence. (I'm a beginner but someone has already answered this and I'm just repeating what was said)