A workplan is a combination
of a schedule
and a resource allocation
table. It attempts to detail what should happen when, and by home.
A good workplan is critical to accomplishing any large project. Creating one will help identify where there are dependencies, give a more complete view of the tasks to accomplish, as well as show where people are being overworked. It also will help show you where you are in terms of both budget and schedule.
A key to success in creating a workplan is to be as thorough as possible. No detail is too small.
A key to success in sticking to a workplan is to avoid scope creep.
Most of my workplans are created using Microsoft Project. I most often refer to the Gantt Chart function.