When customizing a page in SharePoint you quickly run into the fact that customized pages are not loaded anymore from the hard drive but they are loaded from the content database. When you are familiar with SharePoint 2003 you would probably use the terms ’ghosting’ and ‘unghosting’. However since SharePoint 2007 the terms used are customized and uncustomized.
Ghosted / uncustomized files.
These files reside on the hard drive. Typically installed there by the SharePoint setup files. If the files are part from a custom development effort you did, you probably deployed your changes by using a solution package. These solution files are mostly located in a Features folder or in a dedicated folder somewhere in the SharePoint hive, …
Important thing to remember is that these files are on the hard drive and easy accessible with a file explorer.
Unghosted / customized files.
These files are pulled from the content database. Most of the time they are in the content database because you updated the files by using SharePoint Designer.
A typical example is when you adjust a master page in SharePoint Designer and save the changes. From then on, when SharePoint loads a page making use of this master page, the master page is loaded from the content database and not from the filesystem.
This can be confusing sometimes since the file on the hard drive is still present but a different version is used from the content database.
Nice to know.
Since each Web Application has a different content database and customized (unghosted) files are loaded from the content database. It is perfectly possible that one Web Application uses the file from the hard drive (uncustomized/ghosted version) and an other Web Application uses a different version pulled from it’s content database (customized / unghosted).
Also important to note is when you deploy your files with a solution package the files are stored on the hard drive. However when there already is a customized version of a file in the content database then SharePoint will continue to use the customized version. Even if you deploy a newer version to the hard drive after the customization has been done.