It cannot stand alone as a sentence. A phrase is a group of words used as a sentence part. It does not have a subject and a verb. It can be a noun, adjective or adverb. A compound sentence combines two or more independent clauses .
Commas separate the clauses of a compound sentence.
A semicolon can take the place of the conjunction and comma. Only clauses closely related in thought should be joined to make a compound sentence. The conjunction should express the proper relationship between the clauses. And joins ideas of equal importance. Or joins clauses that express alternatives.