The International Building Codes and Fire Code makes an distinction between platforms and stages. This is a very important distinction, as stages have a much larger set of requirements than platforms. With a stage you’ll likely need sprinklers, a standpipe, relief exhaust and additional fire separations from other adjacent areas.
The primary deciding factor that separates platforms from stages, is that stages have overhead hanging curtains, drops, scenery or stage effects. Overhead lights and sound equipment don’t count.
This is only a small part of the code for platforms, stages and assembly spaces but a very important piece.