At one layer, workflow is a platform upon which you can build processes to automate redundant tasks. On SharePoint, workflow is about document and task automation and management. When accessed through SharePoint Designer, workflow can be used to automate a wide breadth of automatable tasks.
You can use workflow to create documents or lists in addition to many other out-of-the-box actions.
You can also use workflow to link SharePoint list data to Word documents.
Logical branches help control when certain workflow actions can occur in a process.
When you include workflow data in an e-mail message generated by a workflow process, you enable rich content in otherwise static text.
With custom form actions, you can create workflow for any data ...