Hi Henry, it is related to the display but it controls how refined the display meshes will be. The display mesh is a triangle mesh that is pre-calculated and stored with an object. Then that pre-calculated mesh is drawn for the display of shaded surfaces.

It can take a while to generate these meshes so it doesn't try to do it dynamically just at display time only. That's for shaded surface display though, curve display is done dynamically during the rendering.

- Michael