Max CPC - cost-per-click suggested by the tool to get first ad position on this keyword. This is a good estimation of what the highest cost per click is for the given keyword.

Avg CPC - average cost-per-click suggested by the tool for highest bidder. Because ads are rotated and bids are automatically lowered to match the next ad, this is the average cost than the highest bidder would pay for one click. This is a good estimation of your average cost for one click.

The CPC rates are guaranteed to be the same as returned by Google Adwords Traffic Estimator tool on the day of compilation.