Typically, manga chapters are serialized in magazines, then collected into volumes—which is how we enjoy them as published, translated content in the West.
Originally a niche genre of graphic novels originating from Japan, the popularity of manga (the correct pronunciation for English-speakers sounds like "MAHNG-a") has exploded onto the mainstream over the last few years. Typically, manga chapters are serialized in magazines, then collected into volumes—which is how we enjoy them as published, translated content in the West.