Bulk Admin: Members of this role can perform Bulk Insert operations on all the databases.

DB Creator: Members of this role can Create/Alter/Drop/Restore a database.

Disk Admin: Members can manage disk files for the server and all databases. They can handle backup devices.

Process Admin: Members of this role can manage and terminate the processes on the SQL Server.

Server Admin: Members of this role can change Server-wide configurations and shutdown SQL Server instance.

Setup Admin: Members of this role can Add/Remove Linked Servers.

Security Admin: Members of this role can create/manage Logins, including changing and resetting passwords as needed, and managing GRANT, REVOKE and DENY permissions at the server and database levels.

SysAdmin: Members of this role have Full Control on the instance and can perform any task.

Public: Public is another role just like Fixed Server Roles, that is by default granted to every login (Windows/SQL)