Authentication and authorization are two essential concepts in application security. Although the terms are often used together, they serve different purposes. Authentication verifies a user’s identity, while authorization determines what that authenticated user can access or do within an application.

Authentication usually happens when a user signs in. The application verifies their identity using credentials such as an email and password, a one-time code, a social login provider, or another authentication method. Once the user has been verified, the application can create a session or issue a token to maintain the authenticated state.

Authorization takes place after identity has been established. An application uses authorization rules to determine which resources and actions are available to each user. For example, both a regular user and an administrator may be authenticated, but only the administrator may have permission to manage users, change system settings, or access protected administrative data.

Applications can implement authorization in different ways. Role-Based Access Control, commonly known as RBAC, assigns permissions based on roles such as user, editor, or administrator. Other systems use permissions, policies, or resource ownership to control access more precisely. These rules help ensure that users can only perform actions they are permitted to perform.

Authentication and authorization work together to protect modern applications. Authentication establishes identity, while authorization controls access and permissions. Understanding the difference is essential when building secure APIs, dashboards, SaaS platforms, and other applications that manage user accounts and protected resources.