Zikten posted...
Omega-Verse is this weird fanfiction thing originally. Where men can get pregnant.
Zikten posted...
(omega means they are super submissive. Opposite of an Alpha)
Weeeeeell, kind of. It's a little more than just mpreg.
Okay, it's a lot more than just mpreg.
It started out in the Supernatural fandom and almost certainly draws ideas and tropes from werewolf fics. Alphas and omegas are primarily differentiated from real life humans by having certain canine-like qualities to their reproductive system. Or to put it bluntly: alphas have knots and omegas periodically go into heat. The latter of which usually creates a kind of sex haze where they're virtually incapable of doing anything else.
While that's generally the extent of the physiological changes for alpha characters, omegas get a bit more. In general, their reproductive system is a lot more feminine in nature. They're capable of self-lubrication and their male bits are often borderline vestigial. It's far more common for omegas to have a cloacal situation, but it's not
uncommon
for them to simply have female bits in place of or in addition to their male ones.
It also isn't necessarily a dominant/submissive thing, though that's often in the mix, particularly during the actual sex scenes. It's instead most common for A/B/O to be treated as a secondary gender. Again, this typically puts the omega in a more feminine light, making them the historically oppressed gender due to being physically weaker and child-bearing. If it's a modern day setting, authors usually just replace the struggle for women's rights with a struggle for omega's rights. Presumably misogyny would not be as big a deal given that women can also be alphas (though being a genre heavily biased towards gay erotica, how female alphas work is usually left to the imagination).
In terms of the weirdness of the Omegaverse, this anime is actually kind of weird in that the protagonist are apparently being judged for being in an Alpha/Omega relationship. In every single Omegaverse story I've seen, this would be the norm. Alpha/Alpha and Omega/Omega relationships would be considered homosexuality with all the possible discrimination that might entail.
There are common variations on all of this, of course (for instance, some works have alphas go into "a rut," their equivalent of a heat), but that's the gist of things.