Examples of these would be heroine, opium, morphine and codeine. An opioid is a synthetic drug made to mimic the
effects of an opiate. These would be
Percocet, Fentanyl, Methadone, Oxy, Demerol, etc.
Opiates are said to be more addictive.
As far as your question about receptors....yes there are differences. I used to say opiate and opioids not knowing the difference until I googled "Opiate vs Opioid" a couple years ago.