what are repocache directories

I run a rsync overnight (during my ISPs free download time) to keep a local
copy of the KDE repositories.
Last night the rsync downloaded over 4500 files including a bundle of
repocache directories containing some oddball file names e.g.


and the like.

What are these repocache directories and the .rpm-* files in them?

If I don’t need them as repos to keep my local machines up to date I’ll
delete them and filter them out of the rsync but I need to make sure first.