Opiods are a class of drugs that act on opioid receptors. There are natural and synthetic opioid drugs, and even endogenous opiods that act on said receptors. Endogenous opiods like enkephalins and endorphins are even blocked by opioid antagonist drugs like naloxone.

If you don't believe me or don't get it, I don't have time to try to convince you, sorry.