Do the common folk of the Forgotten Realms know the difference between fiends? Devils vs Demons vs Yugoloths, etc? Varies very much depending on what local priests, sages, retired adventurers, and gossips tell them. Pretty much "everyone" knows the alignment, political, and summoning differences between devils and demons, but after that…
— Ed Greenwood (@TheEdVerse) January 25, 2018
The common folk get lots of "don't do this, or a devil will–" etc. warnings, but these include exaggerations, deliberate falsehoods ("don't touch my stuff, or–"), and mistakes as well as good advice. And tales ALWAYS grow in the telling.
— Ed Greenwood (@TheEdVerse) January 25, 2018