"They're" is a contraction of the words "they are." It is used to describe a group of people or things and indicates an action, state, or characteristic. For example, in the sentence "They're going to the park," it shows that a group is heading to a specific location. This contraction is commonly used in both spoken and written English. It's important to distinguish "they're" from similar-sounding words like "their" (possessive form) and "there" (referring to a place). Understanding these differences helps in using the correct form in sentences.