Even though I think about Web 2.0, write about Web 2.0, and promote Web 2.0 tools, I still struggle to explain the concepts behind Web 2.0 to educators who have no idea what it is. When their eyes glaze over, I realize that I've already said too much. Is it even possible to explain Web 2.0 in one or at most two sentences? OK, I'd be happy with five sentences. Or five non-threatening keywords, uttered like bullets in a very non-Web 2.0 PowerPoint presentation. I would like to know the shortest, sweetest definitions my colleagues use when trying to explain Web 2.0 to co-workers, students, parents, and administrators. What do you say that turns on a light?