Purpose of 'Re-evaluate Workflow Rules after Field Change'

There is no connection between workflows, and there is no way to control the order of multiple workflows on the same object.  So, if you need 1 workflow to impact another one, make sure the criteria of each workflow takes that into consideration and make sure a Field Update is marked as 're-evaluate workflows'

For Example:

wf1-->type=customer  sets customerdate

wf2-->closedopp>0 and set type=customer

Since you can't control which of these WFRs runs first, you might consider setting 're-evaluate' on the 2nd Field Update to give the first WFR another chance.

NOTE:  This is a simple example to demonstrate the feature -- you would never design Workflow Rules as I have outlined them in this example.