Example: In this example (see the ads at the top and bottom of the page) there are four Banner ads scheduled to appear, but the page is configured to only show 2 ads at a time - so the ads will rotate. Typically, you'll have more ads than space available.
Fixed Frequency: The "Yahoo" ad has been configured to appear each 4th click. With Fixed Frequency an ad will absolutely appear according to the frequency - no more and no less.
Weighting: The "Ford" ad has been given a weighting value of "1". It will always be placed atop the ads scheduled to appear. The ad will not appear more frequently - rather the ad will receive preferred placement when shown.
Rotation: All ads not assigned to a Fixed Frequency will rotate assuring that each ad is seen an equal number of times.