Found:

Restrictive relative clause

GENERAL: Relative clause which is used to restrict the class of entities that can be denoted by a noun phrase. EXAMPLE: in the books that John read, the restrictive relative clause that John read restricts the set of books to those that are read by John. Non-restrictive relative clauses add further qualifications to the reference of the noun phrase but do not narrow down (nor expand) its extension. Thus in this book, which John gave to me, the non-restrictive relative clause does not restrict the set of books. The difference between a restrictive and a non-restrictive interpretation is often only expressed intonationally.