The ad rotation settings determine which ad in the ad group should show. If there are more than one ad in the ad group, Google AdWords will rotate which ad shows depending on the ad rotation setting. There are four rotation settings to choose from: 1) Optimize for clicks – gives preference to ads that expect to attract more clicks than other ads in the ad group, based on historical click through rates. 2) Optimize for conversions – gives preference to ads that are expected to provide more conversions, like purchases and sign-ups, than other ads in the ad group. 3) Rotate evenly – gives equal preference to all active ads in the ad group, regardless of how each ad performs. 4) Rotate indefinitely – similar to the “rotate evenly” setting, this option delivers ads more evenly into the ad auction, but does so for an indefinite amount of time and does not optimize.