The document discusses different types of clauses that are the building blocks of sentences. It defines independent clauses as clauses that can stand alone as a sentence, and dependent clauses as clauses that cannot stand alone and depend on an independent clause for meaning. It provides examples of independent clauses and describes three main types of dependent clauses: noun clauses, adverb clauses, and adjective clauses. It emphasizes that understanding clauses is important for avoiding errors in sentence structure and punctuation.