CPC
CPC stands for Cost Per Click. This is how much you would pay the advertising network every time a visitor clicks on your ad. The CPC can vary based upon your product and your market. Among other factors, the more competition there is in your market, the higher you will probably end up paying.
CTR
CTR stands for Click-Through Rate. This is the percentage rate at which people click on your ad. If your banner ad is seen by 100 people but clicked by one person, your CTR is 1%.
The CTR percentage is calculated by this formula: (Number of Clicks / Number of impressions) x 100