An interrogative sentence is a type of sentence that asks a question. It typically begins with a question word like who, what, where, when, why, or how, or it may start with an auxiliary verb such as is, are, can, or do. The main purpose of an interrogative sentence is to elicit information or clarification from the listener or reader. Interrogative sentences usually end with a question mark (?). They can be open-ended, allowing for a variety of responses, or closed, which typically require a simple "yes" or "no" answer. For example, "What is your favorite color?" is open-ended, while "Are you coming to the party?" is closed.