According to me, they are the same and you can find more information via this thread https://www.webmastersun.com/threads/911-What-is-PPC-
Nowadays PPC is an advertising structure that very effective and popular in internet marketing, we need to know one's way about it
They can be nearly synonymous but CPC is more often used when referring to advertising campaigns you are running as to how much you are paying per click (visitor). PPC is more often used to refer to the general idea of what you are doing. PPC can refer to the always unethical, but not uncommon business of paying people to click on the ads so that the "employer" can receive money from his advertisers.