There's more than one G scale, but there are many scales using the same track, and terminology is inconsistent. 1/32, for which the track represents standard gauge. This is technically called Gauge 1. 1/29, for which the track represents standard gauge (incorrectly). 1/24, for which the track represents... I'm not sure what. 1/22.5, for which the track represents metre-gauge. This is the scale made by LGB, and is one of the two scales that are actually called G. 1/20.3, for which the track represents three-foot gauge. This scale is also called G. I believe the NMRA decided to call it F, but this name hasn't caught on. Often, all of these are collectively called "Large Scale". Sometimes, that term encompasses other scales using different track.