The conversion code can be optionally placed on a 'thank you' page to allow you to track how many conversions your AdF.ly traffic has made.
For example, you are advertising a site that gives away a free e-book on making money on the Internet. You would place the conversion code on the 'thank you' page displayed after the user has submitted their email address.
Now if you have multiple sources of traffic you will know exactly how many of the conversions are from AdF.ly
You can find the conversion code of every campaign you have created by clicking the configuration icon next to your active campaign.