An Eroge (エロゲー or エロゲ erogē, is a portmanteau of erotic game: (エロチックゲーム erochikku gēmu)) or Ero-ga is a Japanese video or computer game that features erotic content, usually in the form of anime-style artwork. Eroge originated from galge, but unlike galge, they feature nudity or sexual content.
Mostly in the form of Visual Novels. There are different types of eroge;
Bl Game; A game focused on two males that.. uhmm.. You know. It does not necessarily have to have erotic content in it, but most of them do. Examples on Bl Games, include; Hadaka Shitsuji, Kuro no Tsuki , And all of Nitro+Chirals games. (Bl stands for Boisu rabbu gamu)
Nukige; There does not have to be a story necessarily to the game.
Nakige; Games that make you cry your eyes out. These games are meant to have an emotional impact on the people playing it. This category includes games like, Clannad, Little Busters! - All of the games made by Key, go under this category.
Otomege; Maiden game. It's a game where the main character is female, and is supposed to get as many guys as possible. This category includes games like; Starry☆Sky, Uta no☆Prince-sama♪ etc. (Many of them get an anime after release of the game)