All sites in SharePoint are the collection of web pages. There are 2 types of concept in paging. Ghosting and unghosting.
SharePoint pages from 2 places on are from database or another one from disk i.e. from virtual path.
Ideally the output will be combination of these both.
2 types of pages available in SharePoint
These are pages loaded from disk. Application pages can be found in Layout folder of hive folder in SharePoint.
All those content generated by users are represent through site pages.
There are types of site pages which include:
Web part Pages: A web part page will allow a user to add web parts.
The other type of site page includes Master Pages.
Concept of Ghosting and Unghosting:
As we know that SharePoint offers 2 types of pages i.e. Application pages and site pages.
When a page is customized in SharePoint designer then for that page all the future exposure will be done from content database. So this process is called unghosting and this page is called unghosted page.
And ghosted pages are those pages whose content does not rendered from content database.
So for this type of pages in content database the row value will be null. So where exactly ghosted page resides, the answer is ghosted pages reside in system disk apace.
The same is called as attached and detached in SharePoint 2010.