A system administrator can view and modify most fields and screens within Matrix. They are automatically given admin permission to all assets in a Matrix website. Still, they cannot edit all fields and screens within system configuration and system management.
The main difference between a system administrator and a Backend user is that you can link a system administrator within the root users group. Doing so promotes the account type to a root user account.
System administrator accounts must be in the System administrators folder within the System management section of the asset tree. If these accounts are not in this folder, Matrix will not consider user accounts as system administrator accounts.
System administrator accounts can create new user account types up to and including other system administrator accounts. This account type can also upgrade user account types lower than their own through the Morph a user account feature.
You can create as many system administrators as you want within your system. You can also link a user group under the System administrators folder to assign all users within the group as system administrators.