The amount of money spent for a click on an ad in a Pay-Per-Click campaign. In the Adwords platform, each keyword will have an estimated click cost, but the prices change in real time as advertisers bid against each other for each keyword. Average CPCs can range from less than $1 dollar for longtail or low-competition keywords, to upwards of $100 per click for competitive terms, primarily in legal, insurance, and water damage restoration industries.
Source: HSMAI CHDM Study Guide