What CPC really tells you
CPC shows the average price of attention: what it costs to get one person onto your site. Because it divides spend by clicks, it lets you compare keywords, ads and platforms regardless of budget size. A low CPC is only good if those clicks are relevant, so always weigh it against the quality of the traffic it buys.
From CPC to cost per result
CPC is the first link in a chain that ends at cost per conversion. If you know your CPC and your conversion rate, you can estimate what each sale or lead costs and set bids that stay profitable. Lowering CPC helps, but improving conversion rate often moves your true cost per result even more.