An HRIS workflow turns an employee request or change into a sequence of assigned actions: gather the required information, route it to the right people, record the decision, and apply or hand off the result. Its value is that a change can be followed from submission to completion without relying on someone to remember the next email.
Consider a department transfer. The request may need a new manager, an effective date, and an approved department assignment. HR must update the employee record, and another service may need selected information. A useful workflow makes those dependencies visible. An approval notification alone does not establish that the employee record or the receiving service has changed.