Here is the explanation of the "Campaign" feature.
Let's say you want to promote your ClixSense affiliate link on two different sites. Instead of using your regular referral link, you can set up two different campaign links to each of them. In this way, you will be able to see which site produces better results for you.
E.g. You want to promote your ClixSense affiliate link on ABC.com and XYZ.com
Then instead of your regular affiliate link which is : clixsense.com/?xxxxxx
you could do this.
Link for advertising on ABC.com : clixsense.com/?xxxxxx&ABC
Link for advertising on XYZ.com : clixsense.com/?xxxxxx&XYZ
Then use each link on the sites you want to promote.
Both clicks and leads (sign-ups) will be counted for you and thus you will be able to judge which advertising campaign was better.