This report helps you track your marketing campaigns - when a visitor comes with a particular URL parameter to your website; you can track the visit from a particular campaign (typically from e-mail or banner campaigns). You can set the tracking parameter in Site Manager -> Settings -> Web analytics.
Detailed information about the Web analytics module can be found in Developer's Guide -> Modules -> Web analytics.
Page url: http://devnet.kentico.com/docs/5_5r2/contexthelp/index.html?campaigns.htm