The verb "Estar" is a Spanish verb that means "to be." It is used to describe temporary states, locations, and conditions. For example, you might use "Estar" to say someone is feeling happy or to indicate where a person is located, such as "Ella está en la casa" (She is in the house). "Estar" is often contrasted with the verb "Ser," which is used for permanent characteristics. Understanding when to use "Estar" is essential for effective communication in Spanish, as it helps convey the right meaning in various contexts, such as emotions or physical states.