What's the different between wikipedia, wikisources, wikibooks, wikinews, wikijunior and wikiversity?

Answer 1

Wikipedia: That famous online encyclopedia
Wikisource: A site that documents uncopyrighted documents (e.g. constitutions)
Wikiversity: Site for learning
Wikibooks: Printed version of any of the "Wikis"
Wikijunior: A proposed series of books for children (learning books - non fiction)

All of which are daughter projects of the Wikimedia foundation,

Hope this has helped,

S.O.