Welcome alfalfa

Just spit out any questions you might be stumped on and we'll try to help.
I'm lost with the rail stuff.
All N Scale is 9mm wide(from inside of rail to inside of rail). Then you have to height of the rail (from top of rail to bottom where it sits on the ties) with code 80 being the tallest. That is the oldest and all brands will run on it. Code 55 is shorter and code 45 is even shorter. The Code 45 and 55 are used to have more life like appearance. The older stock will not run to well on these lower rails do to wheel flangs they used make in the day. They are commonly referred to pizza cutter wheels. They were made with extra big flanges( part of the wheel that rides along the inside rail) to help prevent derailments.
Here in the States most of our stuff is scaled to 1:160 - Japan has stuff that is 1:150 and England has some other 1:148 I think. All these versions will run on 9mm N Scale track. You will have a problem matching Atlas True Track to Kato, because of the plastic road bed connecting system. Micro train should match up to section Atlas track no problem. I'm not sure about Bachmann track, I still never seen a piece in N Scale.