Windows Workflow Foundation makes the creation of applications that contain asynchronous, stateful, long-running, and/or persistent workflows a lot easier. The Windows Workflow Foundation runtime engine manages workflow execution and allows workflows to remain active for long periods of time and survive computer restarts. Runtime services offer functionality such as transactions and persistence to manage errors gracefully and correctly. By the way, the pricing model of Windows Workflow Foundation is rather attractive too: it is free of charge.
Windows Workflow Foundation provides a workflow model that allows developers to describe the processing required by their applications. The model increases developer productivity by creating a greater level of abstraction, and a natural separation of application and business logic from such details as flow control, state management, transactions, and synchronization.