Omegaverse (or ABO) is an AU (alternate universe) in which males can get pregnant. In this system, there are three main roles: Alpha, Beta, and Omega.
Alpha/Beta/Omega or Alpha/Omega (occasionally Alpha/Beta) is a kink trope wherein some, or all people, have defined biological roles based on a hierarchical system, with the terms originating from animal behavior research. There may be a werewolf, knotting, or other animalistic elements involved, or the characters may be otherwise purely human.