The document discusses different types of clauses and phrases that are used in sentence structure. It defines clauses as groups of words with a subject and predicate, and phrases as groups of words related to the subject or predicate. There are two main types of clauses - independent clauses that can stand alone and dependent clauses that cannot. The document also discusses conjunctions that join words, clauses and phrases, including coordinating conjunctions and subordinating conjunctions. It provides examples of dependent and independent clauses and how to properly join clauses using conjunctions to avoid run-on sentences.