Square range ( or actually more like rectangular) is exactly what it sounds like. For civvies, you can only point and discharge firearms in generally one direction. Behind you is the safe zone where people stand and watch, without touching/handling firearms, when you run the course of fire. Some ranges, where safe berms are built up, will allow a slight leeway of some lateral shooting but NEVER breaking 90. You cannot turn with your firearm and point it back from where you came from during a live run. Only when the RO declares the range safe and your firearm is rendered safe can you return to the starting point facing it, obviously with the muzzle controlled in a safe direction.
This does not apply to specific LE or Mil ranges such as Fun House scenarios.