A sentence fragment is a group of words or a dependent clause. It does not have all the components to be a sentence, but can look like one with capitalization and punctuation.
A complete sentence must include a subject and a predicate. The subject must have a main noun and the predicate must have a verb. The noun and the verb are also the simple subject and simple predicate.
Phrase fragments A fragment with only a noun needs a verb. It will need a subject and a verb when used as a complement, object of a preposition, or and appositive.
EX: The broken ipad. The broken ipad sat on the desk.