WF is the programming model, engine, and tools for building workflow-enabled applications on Windows. WF can be used to solve simple scenarios, such as showing UI controls based on user input, or complex scenarios encountered by large enterprises, such as order processing and inventory control.
Scenarios that Windows Workflow Foundation addresses include:
:: Enabling workflow within line-of-business applications.
:: User-interface page flows.
:: Document-centric workflows.
:: Human workflows.
:: Composite workflows for service-oriented applications.
:: Business rule-driven workflows.
:: Workflows for systems management.
Windows Workflow Foundation also provides an extensible model and designer to build custom activities that encapsulate workflow functionality for end users or for reuse across multiple projects.
BizTalk & WF
BizTalk provides developers with the pieces they need to automate business process, while WF is a framework that provides developers with the base components they need to build the modules that will be used to automate these processes. WF provides the ability to more accurately customize these automated processes to your exact business needs.
SharePoint & WF
Although SharePoint Server 2007 provides various out-of-the-box workflows that require no additional attention before using, many processes are very specific to an individual company's needs. WF provides an extensible infrastructure that can be used to create sophisticated workflows allowing you to enable customized workflows that work the way you need them to for the most efficient business operations possible.