Which type of clause modifies a noun and is set off with comas?

A relative clause modifies a noun or a pronoun. A relative clause is a group of Words that includes a verb, but is not a complete sentence, that gives information about the noun or pronoun to which it relates. A relative clause is introduced by a relative pronoun. The relative pronouns are: who, whom, whose, which, that.

EXAMPLES

The runner who finishes first will win the race. (the relative clause is 'who finishes first'; the relative pronoun 'who' realtes to the noun 'runner', modifying the noun as a specific runner)

The one who finishes first will win the race. (the relative clause 'who finishes first' relates to the indefinite pronoun 'one')