Answer:
Sentence fragments are missing either the subject or the verb. For example: "I an apple." is a sentence fragment. It is missing a verb.
A run-on sentence runs on without proper conjunctions or punctuation. An example of a run-on sentence is "I went to the store and I bought an apple and then I went for a jog for a while and then I went home." This sentence is confusing because of its lack of punctuation.