Originally posted by justtakingpics what do you mean "non-destructive"?
Non-destructive means when you are editing an image, the changes you do don't affect the file itself. And you don't have to save a new copy of the file to preserve your changes - the software just always remembers what adjustments you made to each photo, and every time you view that photo, you will see it with your changes intact, and yet if you ever want to go back and revisit your editing for that picture, you will find all your sliders right your left them, so you can pick right up where you left off, or revert any or all settings to their original state. You can also copy settings from image to image, you can batch apply a setting to as many images as you want (say to correct WB for a whole shoot at once) while not affecting any other settings and while still leaving the images "open" for further adjustments - all without *ever* needing to stop and "save" the file or make a new copy of it.
It's the greatest thing since sliced bread. Without this feature, shooting RAW would be a lot more work than it is with this feature. Some programs provide non-destructive editing for both RAW and JPEG, others provide it only for RAW.