ACEO's versus ATC's
I am clear on the fact that ATC's are not to be sold - only traded. So what about ACEO's? What's the difference between an ATC and a ACEO? I see artists selling these "art cards" under the title of ACEO in their etsy shops.
In my research, I read where non-artists were being "left out in the cold" because they didn't have atc's to trade. A group of artists realized this and started making their cards available for sale. The cards are also sold either as originals or editions.
What is YOUR understanding of ACEO's versus ATC's?