What is a workflow? How does Windows workflow foundation WWF helps in simplifying any process?

A workflow is a sequence of activities performed in a specific order.

WWF provides a common workflow technology for Windows, through which each step in a process can be explicitly defined (rather than intertwining its logic in code) and then executed by a workflow engine.

Each activity can be represented by a class, and can per se contain any work that the workflow's creator wants. Activities can thus also be reused across different workflows, making it easier to create automated solutions to new problems.