An otaku is a person who likes staying home all day being overly obsessed with something, such as manga/anime, video games, and even trains.
In Japanese culture, it is considered an insult if you call somebody "otaku", despite they are one. Here are some examples:
- Manga/Anime Otaku: Overly obsessed with anime/manga and collects figures/trophies of various characters.
- Seiyuu Otaku: Overly obsessed with voice actor/actresses (called seiyuus)
- Video Game Otaku: Overly obsessed with video games