A reflexive pronoun is a type of pronoun that refers back to the subject of the sentence. It is formed by adding "-self" or "-selves" to certain personal pronouns. For example, in the sentence "She taught herself to play the piano," the reflexive pronoun herself refers back to the subject she. Reflexive pronouns are used when the subject and the object of a verb are the same person or thing. Common reflexive pronouns include myself, yourself, himself, herself, itself, ourselves, and themselves. They help clarify who is performing the action and receiving it simultaneously.