A user is an individual authorized to log in to a host or vCenter Server.

Several users can access the vCenter Server system from different vSphere Client sessions at the same time. vSphere does not explicitly restrict users with the same authentication credentials from accessing and taking action within the vSphere environment simultaneously.

You manage users defined on the vCenter Server system and users defined on individual hosts separately. Even if the user lists of a host and a vCenter Server system appear to have common users (for instance, a user called devuser), these users should be treated as separate users who have the same name. The attributes of devuser in vCenter Server, including permissions, passwords, and so forth, are separate from the attributes of devuser on the ESX/ESXi host. If you log in to vCenter Server as devuser, you might have permission to view and delete files from a datastore. If you log in to an ESX/ESXi host as devuser, you might not have these permissions.