AfterShot 3 / AfterShot Pro 3 creates XMP files alongside image files.  The XMP is a file that stores the edits to an image file, allowing the edits to be saved without writing any changes to the original image file.  This is called "non-destructive editing". 

Here's more information on non-destructive editing:

http://help.corel.com/aftershot/v3/main/en/documentation/index.html#page/AfterShot-3%2Funderstanding-non-destructive-editing.html