Wall comes from Latin vallum meaning "...an earthen wall or rampart set with palisades, a row or line of stakes, a wall, a rampart, fortification..." while the Latin word murus means a defensive stone wall. English uses the same word to mean an external wall and the internal sides of a room, but this is not universal.[from wikipedia]

A door is a panel that covers an opening in a building, room or vehicle. Doors are usually made of a hard, semi-permeable, and hard-to-break substance (such as wood or metal), but sometimes consisting of a hard frame into which windows or screens have been fitted. Doors are often attached by hinges to a frame. Doors make ingress into or egress from a building, room, or vehicle easier to manage.[from wikipedia]