How commands SVN Diff and GIT Diff work?

Again, the topic is more appropriate for Plugin Development category.

As @Eko-palypse already answered those commands are used to compare file against it’s commited Git/SVN revision controlled version.

@Alan-Kilborn ,

As @Eko-palypse already said Compare plugin can only show the file’s difference (unstaged/uncommited) against the Git/SVN repo.
It is not a revision control plugin.

yes there is a git plugin available but this is not the topic here.
The compare plugin has the functionality to compare the current version against the local git/svn database.

Eko

Is there a git or svn plugin for Notepad++? Is that what is being talked here?

Assuming you’ve cloned a repo locally and changed some code that hasn’t been committed yet,
now when you go to Git Diff, you’ll see the differences from the current code compared to the one in the repo.

Eko