The difference between a clause and a phrase is that a clause contains a subject and a predicate, while a phrase does not. A clause also differs from a phrase because a clause can stand on its own as a sentence, while a phrase can never form a sentence.
Clauses always contain both nouns and verbs. Phrases do not contain both nouns and verbs, instead forming combinations that contain one verb but no noun or one noun but no verb. For example, "best friend" is a phrase that contains a noun, while "she is hungry" is a clause that contains both a noun and a verb. Clauses can express complete thoughts, while phrases can only express additional pieces of information in sentences. Another difference between the two is that phrases are sometimes found within clauses, but clauses are never found in phrases.