auth0 is a cloud-based identity and access management platform that provides a set of tools and services to help developers build and deploy secure and scalable applications. It offers features such as authentication, authorization, and user management for applications, as well as integration with social identity providers such as Google, Facebook, and Twitter. It also provides tools for handling multifactor authentication, single sign-on, and compliance with various security standards and regulations. In short, Auth0 helps developers and organizations ensure that only authorized users have access to their applications and data.