Hi @sumitpatil8983,
Workflow is very vast topic in itself. More & more you start exploring workflows, more & more you be loving it.
It is very difficult to explain workflow alone without Lifecyle Templates, Team Template, Roles, etc...
But to give you a high level idea, workflow system enables you to automate procedures in which information, tasks, and documents are passed among several participants. This procedure is based on a workflow process composed of well-defined steps designed to efficiently accomplish your business goals.
As a starting point, you can start looking at Windchill Basic Administration Guide, page 337 topic "Understanding Workflow".
I hope you will find this as a good starting point. Best of luck!
Regards,
Shirish
