oh god i cant believe im finally an ""expert"" on one of these.
Omegaverse, or A/B/O, was originally a fanfic trope that started out in the Supernatural fandom at its peak. It gained vast amounts of popularity due to the Superwholock boom at the time.
The basic building blocks of Omegaverse were as follows:
-Huamns having a secondary sex, (Alpha, Beta, Omega) which determines their position in sex and how dominant they are. Alphas are the most dominant, Omegas the least, and Betas in the middle.
-Omegas go through a regular heat cycle that can (sometimes) be fixed after being dominated by one of the other Alignments. Alphas will fly into their own heat-like state after smelling the scent of an omega in heat, and cannot control themselves. Betas are not affected by an Omega's heat.
-Alphas have knots on the penis. I dont know why this was the one wolf anatomy thing they decided to keep but whatever.
-During sex, the dominant can mark their partner with a bite, marking the Omega as their mate, and keeping other Alphas away from them.
Since Omegaverse was originally created in a M/M dominated fanspace, there were never any specific rules on how this applied to female or intersex people, and the Beta Alignment was usually thrown off to the side in favor of an Uke/Seme dynamic.
Most works containing Omegaverse contain their own rules, as well as deviating from the original ones. What's important to remember is that this all started because some teenage girl decided her incest fic needed some wolf erotica.