An OAuth application is a third-party software or service that uses the OAuth protocol to request limited access to a user's data on another platform, such as Google, Facebook, or GitHub. Instead of sharing their password, users authorize the OAuth application to access certain information or perform actions on their behalf. This process improves security by allowing users to control what data is shared and to revoke access at any time. OAuth applications are commonly used for single sign-on (SSO), integrations, and enabling secure data sharing between different online services and platforms.