Post-main game, everyone is alive (including Sephiroth) and Jenova has been banished. Not technically an Advent Children AU since there's no Geostigma, it just takes place during the time AC would have.
All of the main events of the game still happened except for the end of Crisis Core; Zack and Cloud chased after Sephiroth together with the rest of the party. Shinra was still destroyed, though Meteor did less damage and Midgar remains intact save for the upper plate. Avalanche (that is, Cloud, Aeris, Tifa, Vincent, and Yuffie; the others do their own thing) lives in a two-story house within walking distance of 7th Heaven. Sephiroth and Zack have another place close by, though Sephiroth's identity is secret to the public. These have a much lighter tone than the other more grounded fics and aren't meant to be taken seriously.

Pairings: Sephiroth x Cloud and Zack x Aeris, and also lot of friendships—you could interpret some fics as Zack x Cloud or Cloud x Aeris if you wanted to. Tifa x Rude mentioned.