A: Uber fan fiction has main characters other than Xena and Gabrielle. These characters can be in any time period, but usually display traits that are associated with X and G. These traits can be physical (hair and eye color), or non-physical (mood, fighting ability, creativity). The characters may or may not be identified as descendents of the warrior and bard.
A: This type of fan fiction is based at least partly on Xena's character from the Hercules episode Armageddon Now part 2. In this episode, Callisto traveled back in time to kill Hercules' mother before he was born. As a result, the big guy wasn't around to help turn Xena from her wicked ways. This led to an alternate future in which the warrior princess took over the entire known world and ruled as a totalitarian tyrant.
A: This variety is basically any story with homosexual content (can range from attraction to...well, consummating the relationship) between two characters. This will usually be Gabrielle and Xena, but can also be any other two characters.
A: The characters of Melinda Pappas and Janice Covington were introduced in the episode The Xena Scrolls as descendents of Xena and Gabrielle. There have been a lot of good stories written about them, but for the most part, these will be of the alternative variety.
A: Crossover stories are when characters from Xena interact with characters from other television shows or movies, Some examples are Xena/Highlander and Xena/Buffy.
A: Beta readers are brave and generous souls who will read your story and help you proofread and edit it before you release it for general reading. To find a beta reader for your story, visit this link.