I was watching the Elegant Universe on PBS, and the show was talking about the string theory. there was one thing that i didnt really get though. It was the relation between strings and branes. I think i heard that if you were to add energy to a string, it gets bigger, and is stretched into a brane. but i'm not sure. please help me understand this. and if what i heard from the show was right, are there differences between the branes formed by open strings and closed strings? please help, am only in grade 11 and understanding something like this will make me seem extremely smart.