Since Google will only show one adUsed to structure your ads, keywords (for search campaigns) and targeting (for GROUP) at a time from an advertiser, ad rotation determines which ad to display if there is more than one ad contained in an ad group. Google Ad Rotations include: optimize for clicksDisplays the ad more likely to receive a click, more often than an ad that’s less likely to receive a click., optimize for conversionsDisplays the ad more likely to result in a conversion (based on conversion tracking) compared to an ad that’s less likely to result in a conversion., rotate evenlyShows ads evenly for 90 days. For example, if there are two ads in an ad group each ad will be shown approximately 50% of the time., rotate indefinitelyShows ads evenly. For example, if there are two ads in an ad group, then each ad will be shown approximately 50% of the time. Will run in this state until you go in and change the settings.