Conversion rate – The number of users who complete your goal (buy your service/product etc) divided by the total number of clicks equal the conversion rate. If the ad gets 200 clicks, and 20 of these result in a purchase, your conversion rate would be 10 percent.
CPA – Cost per Acquisition: This is basically the bottom line .It isthe total cost over a measured period time divided by the number of conversions for the same period.
CPV - Cost per View: For Videos. The advertiser is only charged when a user watches their video.
CPC – Cost per Click:The amount the user actually pays each time a user clicks on their advertisment
CPM – Cost per Thousand Impressions:The amount a user is charge for the ad being displayed. The user bids on blocks of 1000 views.
CTR – Click through Rate: The number of times an ad is clicked divided by the number of times an ad is displayed.
PPC – Pay per Click: The advertisers pay only when an ad is clicked by a user
PPM – Pay per Thousand: Advertisers pay a rate per thousand times an ad is displayed.
Quality Score: Is an estimate of how relevant your ads, keywords and landing page are to a person seeing your ad google
ROI – Return on investment: A performance measure used to evaluate the efficiency of an investment or to compare the efficiency of a number of different investments. To calculate ROI, the benefit (return) of an investment is divided by the cost of the investment; the result is expressed as a percentage or a ratio.