What exactly is a dedicated circuit per code?
Others have pointed out most everything accurately.
I would just add that I've never really seen the term being used to mean anything other than "this circuit is dedicated to this application". It often means it's serving a single load (i.e one copier machine, fridge, etc.) but I've also seen it used to mean its serving more than one load but with the same applications (i.e. clocks, controller, VAV boxes, etc.).