What is the function of Realm in Tomcat?

In Tomcat, the role of Realm is to handle user authentication and authorization. The Realm is responsible for verifying user identity and permissions for access control within the application. By configuring the Realm, Tomcat can support multiple user authentication methods such as database-based, LDAP, JDBC, etc. The Realm can also specify which users have permission to access specific resources, allowing for fine-grained permission control. In Tomcat, customizing user authentication and authorization methods can be achieved by configuring the Realm to meet the needs of different applications.