@K00K13. Your are correct in saying that shoujo is a demographic, not a genre, it refers to media that is aimed at young girls, while Shounen, it’s counterpart, is aimed at young boys, josei at women and seinen at adult males. Usually it means that something like shoujo usually has more romance, Shounen more fights, and seinen and josei more graphic, having things like sex and gore. That’s why these manga genres can have such a range of titles, with titles like Skip Beat where romance plays a big part or Natsume Yuujinchou, a slice of life with supernatural elements that has 0 romance. However bear in mind that what constitutes a work of this genre is not unchangeable throughout time. When Kishimoto published Naruto in Shounen Jump for example, the most popular magazine for Shounen manga, he wanted to do something more like Death Note but was rejected, and years later Death Note was published and nowadays they put in their magazine Chainsaw Man, which has nude lesbians in their cover. So yeah, it’s not a genre but a target audience, whose taste change over time.