There are two main types of clauses: independent clauses and dependent clauses. Independent clauses can stand alone as a complete sentence, while dependent clauses cannot. Dependent clauses are further classified into three types: adverb clauses which indicate time, place or manner using words like when, before, after; adjective clauses which modify nouns using relative pronouns like who, that, which; and noun clauses which function as nouns using words like what, when, why, how. Proper use of clauses is important for clear communication in writing.