as a question adverb (introducing a direct or indirect question): Where are you going? ♦ I wonder where she lives.
as a relative adverb (referring back to a noun and introducing a relative clause): I know a place where you can hide. (introducing a clause that is subject, object, or complement of another clause): ♦ Stratford is where Shakespeare was born.
as a conjunction (connecting two clauses): I’ve hidden the money where no one will find it.