Alexandra Alter at the NYT:
To untangle the Omegaverse fight, it helps to understand its origins in a parallel literary universe — the vast, unruly, diverse, exuberant and often pornographic world of fan fiction.
After getting its start decades ago in “Star Trek” zines, fanfic mushroomed when the internet made it easy for especially dedicated consumers of pop culture to find and create stories for one another. There are now subgenres upon subgenres, from “slash” (where two male characters pair up romantically, such as Sherlock Holmes and Dr. Watson), to odder fare like “mundane AU” (an alternative universe where magical characters live in the real world — e.g., Harry Potter goes to a regular boarding school and has normal teen problems).
more here.