Homeostatic Sexuality is an umbrella term to refer to a "proper" or "natural" mental state of sexuality. It encompasses many different areas, for example it will exclude hypersexuality and exclude hyposexuality. You can think of it like an ideal state. It also excludes various paraphilias. The word is mostly an informal one.
The research indicates all humans are born (nature) with an innate homeostatic sexuality, which largely activates around puberty. Furthermore, paraphilias are not inborn, rather procured due to environmental conditions (nurture).