OAuth (Open Authorization) is a security protocol that allows third-party applications to access user data on another service without requiring the user to share their password. This is achieved by using access tokens, which are secure, time-limited keys issued by an authorization server after the user grants permission. The process involves several steps, starting with the user attempting to access a resource, followed by the client requesting authorization, and culminating in the client receiving an access token that it uses to access the user's resources on the resource server. OAuth enhances security by preventing applications from directly accessing sensitive user data, thereby safeguarding privacy.