In a Simpsons episode of season 25 the dialoge
Monsarno Rep: Say hello to our chief scientist.
Everyone: Augh! Sideshow Bob!
Sideshow Bob: Dr. Sideshow Bob.
Homer: Real doctor or PhD?
Sideshow Bob: PhD.
takes place. In my country there is only a doctor and I thought a PhD would be exactly that in Anglo-Saxon countries. I would like to know is there a difference in the USA between a PhD and a doctor? Especially: What did they mean in the dialogue?
Edit: In hindsight this may be a duplicate, but originally it wasn't because I did not know that the "doctor" of the dialogue was about a medical doctor.