In Sliderule, a workflow is an executable unit of logic. Each workflow is designated a static url, which you can call in order to run the current production logic for that Workflow.
As you change and publish new versions of the workflow, this initial url will remain constant. At any given time a workflow has a "production version" which is the version of that workflow that will be run when hitting the static URL mentioned previously. In order to see the current production version of a workflow, and open the Versions tab