There are several types of curtains used on a stage. Let's take a look at a few of them:
This is the curtain that runs along the proscenium at the front of the stage. It is usually colored and separates the audience from the stage. The Grand Curtain can be set up as a runner (see below), or on a fly line so that it can be raised vertically to reveal the stage.
These long drapes run along the sides of the stage and provide cover for actors and scenery when they are not on stage.
These short curtains run along the top of the stage to hide fly lines, lighting, and anything else that we don't want the audience to see.
This type of curtain travels along a rail or cable system and can be opened and closed at will. Here is a short video showing you how to assemble a simple runner for a small stage: