Stuffing & Dressing
Stuffing and dressing are commonly used as different names for the same thing - a dish consisting of bits of bread (or other starchy things) and various seasonings. The dish can be made by stuffing it (hence the name) inside a turkey or other bird that will be roasted, or by baking or cooking it separately in a casserole dish.
Stuffing dates back to the Roman Empire. The ancient cookbook Apicius de re Coquinaria dates back somewhere between the 2nd and 1st century AD. In there, contains recipes for stuffed chicken, dormouse, hare and pig. Apicius's described ingredients of vegetables, herbs and spices, nuts, spelt/farro (an old cereal grain) and giblets.
The term "dressing" didn't appear until the 1850s, when Victorian nobles took offense at the vulgar word "stuffing." So, it's easy to see why many dressing and stuffing recipes consist of the same ingredients. To understand the difference between the two, all you have to do is look at the cooking method.