Original Murphy bed was stowed vertically in a wall cabinet. The bed disappears entirely when not in use. These have been around since about 1900.
In the RV world, the term is used to describe a bed that folds at least partially head to foot. These do not usually store vertically, unfolded, in a wall, per Murphy's concept and patents. Usually one half the length folds up over the other half, so it takes up more room than the traditional pull-out sofa sleeper, which folds into one third the bed length.