If you're a blogger generating income from your ads, then PPC will mean "pay per click."
However, if you've been a Windows Mobile PDA user for many years, then PPC will mean Pocket PC. Microsoft has a funny way of renaming their operating systems. They can't seem to make up their mind about nomenclature. Windows CE evolved to Pocket PC which then turned into Windows Mobile and now we'll have Windows Phone (what about those PDAs that aren't smartphones?).