Typically you'll undertake marketing activity where you want to communicate with a targeted group of People / Organisations / Leads, based on a shared attribute or group of attributes.  For example, you might be releasing a new product or service and want to communicate with all the People who have already bought from you.  

Workbooks enables you to create a Marketing Campaign and add 'Members' to that Campaign.  The Members are your target audience, ie the People / Organisations / Leads with whom you want to communicate.  

Most commonly the list of members is created by first generating a report that identifies your audience, although you can also add new People / Organisations / Leads individually. When adding People or Leads to a Campaign, that Person or Lead's email address can be used to send a mailshot.

Organisation records in Workbooks don't include email addresses so the usual purpose of adding them to a Campaign is to call the Organisation in order to find out who the right Person is to contact there.

You can record the Campaign dates, the budget for the Campaign, the target revenue to be generated and the goals for the Campaign as well as creating Notes and Activities associated with that Campaign.

The success of a Marketing Campaign can be measured by mapping results to goals so you can get real-time information on the status of your Campaign and get accurate feedback about the return on your marketing investments.  You can also run reports on Campaign data to work out, for example, the cost of Leads generated per Campaign.

You can send Mail Shots to the Campaign members, so you can easily target your marketing. 

As your Campaign runs it generates Leads and Opportunities.  These are recorded on the Campaign record, which allows you to analyse the success of the Campaign.