What does this mean contains a fragment?

In English writing, there are complete sentences (thought) and incomplete sentences which are called fragments. We must use complete thoughts to communicate well and to be understood. Teachers might write "contains a fragment" on a student's paper to draw attention to a "sentence fragment" that needs fixed to make it a complete sentence.

Some examples of incomplete sentences or "sentence fragments" are these:

• Teachers might. (Might what? There's no sentence object here.)
• What does? (What does what? The sentence needs an object.)
• Pushed the vacuum cleaner. (WHO pushed the vacuum cleaner? The sentence needs a subject.)
• Jumped off. (Who jumped off what? The sentence needs a subject and an object. For example: The cat jumped off the table. The boy jumped off the four-foot high wall.)