A documented task is often referred to as a Use Case. “The use case technique is used to capture a system's behavioral requirements by detailing scenario-driven threads through the functional requirements.”1 In other words, the objective is to define how (step-by-step) a particular persona might go about performing a task on your site and what is required to complete the task.

1. 1. Wikipedia.org, Use Case http://en.wikipedia.org/wiki/Use_case