A backdrop is a painted curtain that hangs in the back of the stage to indicate scenery. Before the advent of motion pictures, theaters would have 6-8 stock painted backdrops on canvas for use in live theatrical performances. Often these would include an urban scene, a nature or garden scene, and a domestic interior.
Drops may be hung by various means. Often made of muslin which has been sized and painted, the top may be pressed between two pieces of lumber (a batten) and clamped to a pipe, with a pipe or chain through a hem pocket at the bottom giving it weight to prevent flapping. Some may be grommeted along the top and tied to the pipe with tie-line (usually drapery cord nowadays). A time-honored method of hanging a drop is the roll-drop, in which the bottom of the drop is attached to a round batten. The drop is rolled onto it from the back, and is deployed by rope rigged through blocks (pulleys) to be pulled from offstage to release the tension holding the batten up, thus unrolling it slowly until completely unfurled.
There is also a form of drop used in Vaudeville days, which may still be seen in older theaters, called an olio. “Olio” means conglomeration, and these drops were most often roll-drops covered with advertisements from various sponsors, for the audience to view between shows.