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.
Here is the example of Max and Avg CPC: Note: This is just an example, don't use this in real life.
Max CPC
AVG CPC
Keywords
520.52
97.44
domains yahoo
418.63
79.81
domain name yahoo
145.71
68.91
dc hair laser removal washington
119.63
66.15
law lemon wisconsin
135.94
51.14
hair removal washington dc
493.73
41.97
domain registration yahoo
This means if your site has these keywords and somebody click on it, you will get max CPC and avg CPC above