You can likely guess what the genre known as "ecchi" contains, by this point. If it's sexy, naughty, risque, and/or flirty, it's squarely ecchi.
Ecchi is another way to say "perverted" in Japanese, but its connotation is not as strong as hentai. Anime that contain a lot of sexual humor but no outright pornography are often referred to as ecchi, examples include Love Hina and to a lesser extent Ranma 1/2.
Harem is a kind of story in Japanese anime and manga where a male character is surrounded and loved by many female characters. Suzuka, Love Hina, Ai Yori Aoshi, Rosario + Vampire, Highschool DxD and Sekirei are just a few examples. Most of the time the females are romantically interested in the main character.
Original video animationOriginal video animation (Japanese: オリジナル・ビデオ・アニメーション, Hepburn: orijinaru bideo animēshon), abbreviated as OVA and sometimes as OAV (original animation video), are Japanese animated films and series made specially for release in home video formats without prior showings on television or in theaters, though the first ...