Is It Called Stuffing Or Dressing?

Thanksgiving is next week and my annual state of confusion will soon be starting. I grew up with a mom who called the stuff you put inside of the turkey 'dressing'. To make things all the more confusing, my grandmother has always called the dish 'stuffing'.

So, I call it a mixture of the two depending on who I'm talking to and I never know if I'm saying it right. I can't be the only one who has no idea what the difference actually is. I've even Googled it...and Google has been no help.

I totally understand why it makes sense to call the dish stuffing when you're putting it inside of the turkey. But, if you're not putting it in the turkey, then it doesn't make sense.

So maybe that's it how you decide? Inside of the turkey is stuffing, outside of the turkey is dressing? I have no idea. I need your help. Is it stuffing or is it dressing? Are the two terms interchangeable like hot dish and casserole?