Finally, what is a "metadata" edit? Is that a disphemism for a "global" edit?
I think to answer that, someone would also have to explain what metadata is.
Metadata is data that in itself isn't the data you're looking at, but rather data about
the data, so to speak.
For instance, in this post, it's:
- the posting time
- the nickname of the poster
- the thread name
- the board name
- various other identifiers
In an image, it is e.g. the exposure, the time of capture, the white balance, the image dimensions, etc. Changing these values does not necessarily change the image, but it can change how software chooses to interpret the image data.
So a "metadata edit" is simply an edit of these additional data about the image, and not the pixel values.