Request status can change as a request moves through its resolution process. Each request status can control request field attributes, such as whether or not a field is visible, editable, required, optional, and so on.
Request status can be tied to a workflow step, so that when a request reaches a certain workflow step, it acquires a status that changes the attributes of a field. The request status at a given workflow step can also drive field logic during the life of the request.
Typically, a given request type is associated with a single workflow. Information contained in the request (defined in the request type) works together with the workflow process to ensure that the request is correctly processed. Although you can use one workflow with many different request types, the level of possible integrations between request type and workflow is easier with a one-to-one mapping.