There are four main types of sentences: declarative, exclamatory, imperative, and interrogative. Declarative sentences make statements and express opinions, ending with a period. Exclamatory sentences express strong emotions like disbelief or happiness, ending with an exclamation point. Imperative sentences give demands or instructions, sometimes ending with a period or exclamation point. Interrogative sentences ask questions, ending with a question mark and using question words like what, when, where, why, do, or how.