UNIX for Beginners Questions & Answers

I had to add extra asterisks because when I ran the original code, it added 'DWI_dti_fa.nii.gz' instead of '111180_dti_fa.nii.gz'. I'm guessing the extra asteriskts told it go one folder further. How does that part of the code work? Is it recursively looking into folders..I ask because I've also seen it done using just ** with globbing so I was just wondering what the difference was and why it works. Actually, if you could explain the code, what TMP, FN, %% etc all do/stand for that would be super helpful so I could learn.

I was a bit sceptical when I saw your file name samples like home/user/... guessing it should be /home/user.... That's where the "additional" level came from.

find traverses the directory tree starting at the given dir looking for regular files (-type f) and all files matching the pattern given, printing the full path to stdout. For further details see man find.
stdout is piped into a shell while loop that reads the full file name into the FN variable. TMP is another temporary shell variable that is assigned from FN using shell's parameter expansion (see e.g. man bash). # removes shortest matching prefix pattern, %% removes longest matching suffix pattern. /.../... does pattern substitution.