This article explains what marketing campaigns are and why you would use them.
Marketing Campaigns give you the ability to track how your customers are finding you - through what marketing activities you are investing in.
For example you may invest in certain marketing activities for example, facebook advertising, the creation and maintanence of your own website, word of mouth, and yellow pages.
In order to see if you obtaining the benefits from these marketing activities or where the majority of customers are finding you - you should be tracking this and the income that is generated from these marketing activities.
Marketing Campaigns gives this ability within Actionstep.