What is Destructive Editing?
Destructive editing refers to modifications to a piece of data that permanently modify the data. It's also called a destructive operation. Permanent, in this sense, means that by default no copy of the original data is kept, and if it's kept, it's in the undo history that is temporary. The opposite term is non-destructive editing, which keeps the original data and applies modifications to it when displaying the data, such that the modifications can be easily toggled on and off.
A simple example is making an image greyscale. In destructive editing, this removes the color of the image's pixels so you can't get it back later without undoing the operation. In non-destructive editing, it merely applies a filter to the colored image that is applied before the image is displayed and can be toggled on and off.