Utilitarianism is a teleological ethical theory that evaluates actions based on their consequences. There are three main types: act, rule, and preference utilitarianism. Act utilitarianism judges each act independently based on its consequences, while rule utilitarianism evaluates actions based on general rules that maximize well-being. Preference utilitarianism focuses on fulfilling individual preferences and interests rather than maximizing happiness. Utilitarianism faces criticisms such as the naturalistic fallacy and the inability to accurately quantify and compare pleasures. Rule utilitarianism is argued to be more practical than act utilitarianism as it provides stability of rules and obligations in society.