The other name for a relative clause is an adjective clause.

No, "were" is not a relative clause. "Were" is a past tense form of the verb "to be" and can be used to form the past tense of a sentence or express a conditional statement, but it is not used to introduce a relative clause.

It is a free relative clause, also referred to as a headless relative clause.

an adjective clause.

A relative pronoun usually introduces a relative clause, which provides additional information about a noun in the main clause. The relative pronoun connects the two clauses and acts as the subject or object of the verb in the relative clause.