This type of manga translates as "fan-work" (literally "same-person-writing")
Doujinshi is unofficial manga that is made and produced by fans of an original series, or a self-published manga.
Gekiga means "dramatic pictures". This type of manga is more experimental or literary.
This manga is sexually hardcore manga. Hentai is Japanese for "perverted" or "perversion". (adult content)
Josei is manga aimed at adult women. (adult content). It is derived from the English "Lady Comic"
Seinen (literally "adult") is the exact same thing as Josei except for males. (adult content)
Shōujo (literally "young girl"), Not Shōjo(処女）, shojo means virgin、
is manga aimed at young females up to the age 18. These series tend to
focus on romance and relationships from a young female's point of view.
This is almost the same as shojo except it is mostly action, sports
or romance for males up to age 18. It translates literally as "boy".
This kind of manga is for little children that are just learning to read. Kodomo translates literally as "child".
Shōujo-ai / Yuri
This manga is based on female/female romantic relationships.
Shōuo-ai translates literally as "Girl-love", though it should be noted
that in Japan itself, this term has a different meaning, referring to
pedophilia. Yuri translates literally as "Lily". In Japan, the term GL
(Girl Love) is sometimes used.
Shōnen-ai / Yaoi
This manga is the same as Shōjo-ai / Yuri except it's boy/boy
relationships. Shōnen-ai translates as "Boy-love" (same disclaimer as
for shōjo-ai). Yaoi is an acronym of yama nashi, ochi nashi, imi nashi (no climax, no punch-line, no meaning). BL (Boy Love) is sometimes used in Japan for this type e.g Matt Friend and Dan Vought.