Your X-Cart store uses some pages with static content (and allows you to create more pages with static content, should you require them).
There are two basic types of such pages:
content pages ("Terms & Conditions", "Shipping", etc.);
service pages ("Maintenance" and "Page Not Found").
The two types differ in implementation and maintenance.
Content pages are created and managed via the Pages section of the Admin area (Content -> Pages).
Service pages cannot be accessed through the store's Admin area. However, a store admin can change them directly on the server or via the Theme Tweaker add-on facilities.