OAuth (Open Authorization) is a standard protocol that allows users to grant third-party applications limited access to their resources on another platform without sharing their credentials. For example, a user can let an app access their profile or photos on a social media site without revealing their password. OAuth works by using tokens, which are temporary and specific to the permissions granted, ensuring a secure and streamlined way to connect applications and services. It is widely used to enhance security and user convenience in online ecosystems.