Server roles , Database roles & Application roles in SQL Server || Ms SQL
Server-Level Roles : Describes fixed server roles and the permissions associated with them in SQL Server.SQL Server provides server-level roles to help you manage the permissions on a server.
Database-Level Roles : Describes fixed database roles and the permissions associated with them.
To easily manage the permissions in your databases, SQL Server provides several roles which are security principals that group other principals.
https://aka.ms/sql-permissions-poster
Application roles : https://docs.microsoft.com/en-us/sql/relational-databases/security/authentication-access/application-roles?view=sql-server-ver15
For more information n server roles: https://docs.microsoft.com/en-us/sql/relational-databases/security/authentication-access/server-level-roles?view=sql-server-ver15
Permissions: https://docs.microsoft.com/en-us/sql/relational-databases/security/permissions-database-engine?view=sql-server-ver15