actually you can use them as very,so, a lot. there's no differences, especially when you use them as adverbs. but be careful. 이 음식은 정말/아주/진짜/매우 맛있다.(this food is so delicious.)all of them are okay. 그의 말은 진짜/정말(이)였다.(he was true.) 아주,매우 are not okay. 그 다이아몬드, 진짜니?(is that diamond real?) 아주, 매우, 정말 are not okay.

진짜 and 정말 means " really " 아주 means " verry " for 매우 i don't know exactlly what it means :)