Using That or Which

That and which can both be used to introduce a relative clause that gives additional information about a place, thing, or idea.
 

The relative pronoun that introduces necessary information about things, people, places, and ideas. It introduces a restrictive clause. The meaning of the sentence would change if that clause is taken out.

The relative pronoun which introduces unnecessary information about things, places, and ideas. It introduces a nonessential clause. The meaning of the sentence does not change if that clause is taken out—the clause is providing extra information.