You can add tags to the end of affiliate links. If you aren't using a link campaign then there needs to be a zero in that space.
Here is the breakdown of an affiliate link:
Example link with custom tag "whatever-custom-123":
Custom tags may contain ONLY letters, numbers and dashes. No underscores or spaces.
You can use this for advanced affiliate tracking because the custom tag is logged in the system and is viewable on the link campaigns listing page.
Additionally as a publisher, you can have the system add the variables to the end of the Landing Page Redirect URL for affiliates. The custom tag is optional and is added as a variable called custom_1 if present.
First, make sure you have "Append affiliate variables onto redirect URL query string" checkmarked on the Edit Pricing page.
Example affiliate link:
One possible use for this is that you can use this to allow your affiliates to point traffic to different landing pages. (You would need to make your redirect script point to these various landing pages based on the incoming "custom_1" variable). (You would of course need to notify your select affiliates of the particular tag to use.)
Keywords: Affiliate links