what is the difference between a workplan and a timeline?

Answer 1

A workplan is usually something that has not occurred yet. It's a plan for something you are about to do and you set it up with a time schedule. It's kind of like a teacher's plan book for a week. It gives you an idea of how much time it will take you to reach a particular goal for a project.
A timeline is a record of events that have already occurred in chronological order. You might see timelines depicting the journeys of all the explorers showing when the important discoveries took place. Another timeline might depict space exploration etc.

Hope this helped.:)