There are 2 types of pages in SharePoint.
- Ghosted pages
- Unghosted Pages
Content pages which can not be customized are called as ghosted pages. This page does not really exist as a single entity, it’s the combination of physical page template and a set of content from the content database. Ghosted pages are retrieved from file system when requested.
Ex: Application pages are always ghosted pages.
Application pages reside in SharePoint root folder or SharePoint hive or 15 hive, the path is %COMMONPROGRAMFILES%\Microsoft Shared\WebServer Extensions\15.
Content pages which can be customized are called as unghosted pages. Administrators and Power users can use SharePoint designer to customize content pages within a site collection. If this customization includes changes to the physical page template, the becomes the unghosted. The entire ASPX page resides in content database and retrieved when requested.