Campaigns are simply a means of grouping your traffic for stats reporting. You can create as many campaigns as you would like and name them as you see fit. You might have a campaign for exit traffic, each of your sites, purchased traffic, etc. If you do not wish to use campaigns you can just choose Default. The default campaign can be used as a normal campaign and will always exist.
We also support auto campaigns, which comes in handy when you need to track a lot of links/ads/zones and don't want to setup each campaign manually. You can do this by adding ?autocamp=XXXX behind any linkcode.
For example you could add ?autocamp=sitename_source_zone_ad_no behind your linkcode which will automatically create a campaign named "sitename_source_zone_ad_no".