Non-destructive Editing
An approach in which adjustments are stored as instructions rather than being written into the pixels of the original file.
In depth
Because the original data is never overwritten, any decision can be reversed or altered months later, and the same source can support several different interpretations at once. It also keeps quality intact: a series of destructive edits compounds rounding errors, while a non-destructive stack is computed once from the original.
Examples in practice
Changing the white balance on a file edited two years ago works exactly as it would have on the day it was shot.