Her is a pronoun used to refer to a female person or animal that has already been mentioned or is understood from context. If you're talking about your friend Sarah and want to avoid repeating her name in every sentence, you might say “I saw her at the library” or “That book belongs to her.”

Her works in two main ways. When it's the object of a sentence, you use her: “The teacher called on her” or “Give the ball to her.” When showing possession, her means something belongs to a female person: “her backpack,” “her idea,” or “her turn to choose the game.”

Compare this to he and him, which work in similar ways but refer to males, or they and their, which can refer to anyone regardless of gender. Sometimes people avoid using gendered pronouns by restructuring sentences or using they instead, but her remains one of the most common words in English. You probably use it many times every day without thinking about it, smoothly keeping conversations flowing without repeating names over and over.