A user is an individual authorized to log in to either an ESXi host or vCenter Server.
ESXi users fall into two categories: those who can access the host through vCenter Server and those who can access by directly logging in to the host from the vSphere Client, a third-party client, or a command shell.
The user list that vCenter Server maintains is separate from the user list that the host maintains. Even if the lists appear to have common users (for instance, a user called devuser), treat these users separately. If you log in to vCenter Server as devuser, you might have permission to view and delete files from a datastore, whereas if you log in to an ESXi host as devuser, you might not.
Because of the confusion that duplicate naming can cause, check the vCenter Server user list before you create ESXi host users to avoid duplicating names. To check for vCenter Server users, review the Windows domain list.