Document Handlers
The Document Handlers section of the Gnome Control Center allows you to change the way certain file types and functions are viewed, edited or manipulated.
Default Editor
The Default Editor Capplet allows you to select which editor will be your default editor while using Gnome. This will allow applications like the Gnome File Manager to launch the correct editor when you try to open files associated with editing. All popular editors available are included in the selection list.
File types and programs
This section allows you to configure how files of various types should be handled. File type (formally called MIME type) describes what kind of data and in what format the file contains. For each of the file types, you can set the icon to be used by the File Manager, the default application to be used to open files of this type, etc. For example, file type image/jpeg is used for image files in JPEG format; by default, it is opened using File Manager's built-in graphics viewer.