The document discusses different types of sentences in English grammar. It describes four types of sentences based on structure: simple sentences containing one independent clause, compound sentences containing two or more independent clauses joined together, complex sentences containing one independent clause and one or more dependent clauses, and compound-complex sentences containing at least two independent clauses and one or more dependent clauses. It also outlines five types of sentences based on purpose: assertive, interrogative, imperative, optative, and exclamatory sentences.