It is a web service that makes it easy to coordinate work across distributed application components.

Think about an expense report that you submit. It may require a report that you submit. It may require 3 approvals you submit. This would be the job of SWS, you can create a workflow to get approval from manager 1 and then send it for approval to manager 2 and then 3. When the workflow is completed it could even trigger an email notification to you.