A significant number of traditional theatre stages slope down towards the front of the stage; this is called a rake. It helps to improve sightlines for those sat in the stalls, but was originally a Victorian invention to aid false perspective. It can also cause problems for props / scenery on wheels. Temporary rakes are sometimes built as part of a set design.

The terms upstage and downstage derive from this layout. Also, for one actor to "upstage" another, he can move upstage and therefore be physically higher.

See Also

Defining the Stage