Do Shojo and Bishonen overlap, or are they seperate?
Shoujo is a genre of manga/anime targeted at girls. There's an explanation here that covers it, but basically, it's manga/anime where the target demographic is 8-17-year-old girls.

Bishonen is an aesthetic/style that refers to pretty boys, who generally have feminine and delicate features. It most often shows up in shoujo and yaoi manga/anime, but it isn't exclusive to them. An entire manga/anime can be drawn in the bishonen style or individuals can be. (Wikipedia)