I will be Письмо these Статьи to help people with Аниме terms they do not understand. I will try to use two terms that are semi similar to eachother.

Part one harem and male harem

Male harem или reverse harem
Is a story revolved around a girl where quite a few handsome guys fall for her all at once. While it is partly funny it s usually a strict cheesy romance. Depends on the Аниме but it almost always has guys running around without shirts so consider it perverted regardless of Популярное belief. The most Популярное is vampire knight.

Harem is a Аниме revolving a guy with a similar problem. Harem are usually super funny with perverted comedy with a hint of comedy. Often the guy is clumsy and gets himself beat up for accidental harassment или something.
The main girl often has розовый hair and a clueless attitude. They are almost all ecchi for the reason of having perverted humor and funny moments. The most Популярное is rosario vampire.