The administrator is a user role in WordPress. You will be assigned the admin role when a user installed WordPress and creates a username with their own password. The user who manages WordPress will have access to all the capabilities and actions of his site.
A user who is the administrator can also delete and add other users with the same role. The administrator is the only user who has the power to update a WordPress blog. You can edit core files and change WordPress themes using the built-in theme editor. He can also modify add and remove any plugins.
As a general rule, there is usually only one administrator, in the case of a multisite installation of WordPress, some of the capabilities of the role are assigned to a super administrator. While the administrator roles would only take care of managing a single site, the super administrator could bring in new users, modify themes, add and remove plugins, and manage the site network.