Space Administrator Permissions
A member of the space administrators group (space-administrators) has a number of privileges/responsibilities that affect the entire space including assigning space and page permissions. Select the Space Admin option in the Browse link in the Confluence header to view what a space administrator can do. See the Atlassian documentation for more information about Space Administrators and their permissions.
You can click on the Permissions link under Security to add/remove permissions for this space. This screen shot is the default space permissions for a space.
Any changes to the permissions will impact the whole space. Page restrictions override space restrictions, i.e., if userY belongs to the space-users group with view access to all pages in the space, a page was added by a member of the space-administrators group and restricted to userX for viewing permissions, then userY can not view or edit that page.
Themes control the look and feel of the space. The Theme can be changed at any time by a member of the space-administrators group.