Dumb question - what is meant by 80-85% Mauser?

[Zonaken]

Quoting from another thread, I read "Look for like a 80-85% Mauser and then it still has collectable appeal...."

Pardon my ignorance, but does this refer to the finish or the quantity of matching parts? ...or something else?

Thx in advance.
Zk
flunked pre-school at Luger University...