How do text ads cycle through the search result pages?
Text ads are positioned on search results pages based on their Ad Rank. The main components of Ad Rank are your bids, the quality of your ads, and website, as well as the expected impact of extensions and other ad formats. The ad with the highest Ad Rank appears in the first eligible position on the search results page. The ad with the second-highest Ad Rank appears beneath it, and so on down the page. Learn more about ad position
AdWords recomputes the Ad Rank for your ad on every page, and it takes into account whether your ad was shown on a previous page. This means that your ad may sometimes appear in a top spot on one page and then again in an "Other" spot on a subsequent page (or vice versa).