This tab is available only if the Show Global Privileges checkbox in the Administrator section of the Options dialog has been checked.

Under Assigned Privileges, you find the global privileges assigned to the selected user. For more information about those privileges, see Privileges Provided by MySQL. Global means that those privileges apply to the MySQL server in general (like the Shutdown privilege), or to all databases on the server (like the SELECT privilege).

Privileges not assigned to the user are listed under Available Privileges. You can remove privileges by selecting them in the left box, and then clicking the > button. Removed privileges will appear in the Available Privileges box. You can assign privileges by selecting them in the Available Privileges box, and then clicking the < button.