@FeudMaster the line is drawn between Ecchi and Hentai. Ecchi is sexually charged and very suggestive, almost always showing nipples. Although some ecchi series censor the nipples and such. On the other hand, Hentai almost never has qualms about showing straight up sex, with genitalia in the frame.
Additionally, there is the smut genre, in which sex happens, but the genitalia are not visible through in frame censorship or simply by being out of frame.