The document discusses two types of sentence problems: fragments and run-on sentences. It provides examples and explanations of each, along with methods for correcting them. Fragments are groups of words that resemble sentences but are missing a subject, verb, or both. Run-on sentences incorrectly connect two independent clauses without proper punctuation. The document demonstrates how to fix fragments by adding the missing elements, and how to separate run-on sentences by punctuating between the clauses or joining them with a conjunction.