Blender on Linux and User Preference Question

I use Blender on Linux Mint 14 and I save often on various projects that I am working on.

Whenever I save a .blend file (ex. project.blend) I get an additional file saved (ex. project.blend1 or project.blend2),

Question:
Can anyone tell me why this happens and how this works?

I have also been using the User Preferences a lot because their are some customizations that I always use (ex. zoom with mouse) and whenever I start a new .blend project I have to manually enable this feature because by default Blender won’t save past User Preferences.

Question:
Can anyone tell me if there is a file within the blender source that I can save that controls a particular User Preference setup that can always be switched in and out with the default User Preference file in the event that a past customization can be used in the future?

Question:
Can anyone tell me why this happens and how this works?

File saving
http://wiki.blender.org/index.php/Doc:2.6/Manual/Data_System/Files/Save
http://wiki.blender.org/index.php/Doc:2.6/Manual/Vitals/Undo_and_Redo#Save_and_Auto_Save

Richard,

You are a human Blender encyclopedia.