"powerhead" and a regular "pump"?

[boatload]

what is the difference between a "powerhead" and a regular "pump"? I recently was in a Worm's Way retail store, and asked the clerk, and his answer was "Hmmm, I think they are the same."

I thought I would call on the collective expertise of the group (and Ron).

Thanks a boatload.

[Ron]

A power head pump injects air bubbles into your water at the same time as it pumps water.