Thanks, video number 7 is helpful, but I still don't understand the rotation. If the auction happens just like explained in that video, users would almost never see the banner on a specific site change during a visit. Since the advertiser's ad rank is unlikely to change dramatically during a single visit, that same advertiser will keep winning the auctions for each impression. However, this obviously isn't the case since the ad shown usually change for each new impression.
So in the video he gave the example of advertiser's A & B. Advertiser A had an ad rank of 24, while B had an ad rank of 21. This means that advertiser A pays $1.76/click and wins the auction. If in this same scenario advertiser B's ad gets shown instead of advertiser A, do they also pay the winning bid of $1.76, or do they just pay the minimum CPC?
If I am looking at this wrong and only the ad with the highest ad rank wins the auction and gets shown, then how does Google prevent users from seeing the same ad over and over on a visit to a particular site?