Shoujo manga refers to manga whose readers are primarily young girls, aged 10-18 years. The story plot usually about love and romance relationship, but it’s genre is not limited to school romance per se, it could extend to science-fiction, sports, historical, etc. But majority of shoujo manga have classic drawing styles, such as pretty girl with big-rounded eyes and beautiful boys, although it doesn’t apply in all of them.
Examples of popular shoujo manga are :
Sailor Moon by Naoko Takeuchi, 1993.
Hana Yori Dango (a.k.a. Boys Over Flowers) by Yoko Kamio, 1995.
Fruits Basket, by Natsuki Takaya, 2001.