slashfest is a give a scenario and then someone writes it multi-fandom type thing.

So, say you want to see a Luke/Wedge lovefest, you'd request that. Then, people from all these fandoms would be all YAY, I'll write it. Then, they have a certain amount of time to write it in.

That's the quick quick version of it. I'll be posting more info as the start time gets closer.