What does project switch in Workflow settings do?
Instead of viewing workflow as a board or a sales pipeline, you can view it as project with specific set of actions that need to be completed. This is used with recurring deals that should be kept in check on regular basis (in accounting for example).
In workflow settings you will just turn the Project switch on and workflow view will be changed.
Instead of viewing deals in Board view with stages like this:
all deals in Project view will be placed on the left side, and stages will be listed as actions you complete for each of them.