"Oxygen free copper" is a form of copper, nearly pure, that is used for wires. No other form, AFAIK, is used for electrical wires.
It does differ from 'simple' copper; I can attest that it is noticeably harder to machine than other forms of copper.
Also, AFAIK, this level of purity is difficult to achieve in recycling, so wire is made from "virgin" copper ore only.
