A campaign is a scheduled sequence of events enacted upon a target audience of prospects. The audience is defined by lists that are created in the list builder, associated forms, and other campaigns using the 
Add to Campaign Action.
The overall sequence of events is defined by a course of one or many flows, each flow containing one or many Actions. As prospects travel through one flow at a time, they pass in and out of various Actions. Each Action performs a specific operation on the prospect.