fragment occurs whenever you do these three things:
You begin a group of words with a capital letter.
You conclude this group of words with an end mark—either a period [ . ], question mark [ ? ], or exclamation point [ ! ].
You neglect to insert a main clause somewhere between the capital letter at the beginning and the end mark concluding the word group.
Every sentence must have at least one main clause. A main clause contains an independent subject and verb and expresses a complete thought. Once you have a main clause, you can then add other grammatical elements, but you must have the main clause as the base of the sentence.