In addition to the site-wide permissions, the system administrator can assign permissions to the user roles at the application level for all applications at the site root, and then again for individual applications.
For example, the system administrator configures the default settings for the site wikis on the Default Permissions page.
As the system administrator or wiki administrator adds wikis to the site, users inherit the permissions specified at this level and override any conflicts with the site-wide permissions. When modifying an individual wiki, the system administrator can specify additional permissions.
No default permissions are specified at this level. If no roles are added or modified, users inherit the permissions set for all site wikis.
More about application-level permissions: