There is a difference between scale and gauge. The gauge refers specifically to the distance between the rails, and then even the rails have different codes in the scales.
Say what?
In scale, the engines, cars, and even the rail heights (the code part) and the distance between the rails should very closely scale out to the real items they are meant to depict. Gauge is the distance between the rails, and there were many gauges over the years. You can have the standard gauge we see all over N. America, but there are "narrow" gauges, too. The famouse White Pass and Yukon in Alaska is an example of a narrow gauge, as is the Durgango & Silverton. They have essentially full-sized engines and rolling stock, but the wheels are set closer together.
HO scale is "half O" in gauge, or very closely, but whatever O was and HO had to be to be "half O", the resultant model trains had to match the size of the prototype engines that would have had axles and wheels capable of using the scale distances between the rails. You wouldn't have rails so far apart, but put a 100 pound monster 2' tall and 4' long on those impossible scale rails, right? The engines have to look like a smaller version of the real thing.
O gauge trains are very nicely detailed and easy to see, but the High Rail or tinplate versions, three-rail, can run the gamut of being very toy-like to being very costly and nicely appointed. Whereas the vaious "scales" are meant for a market that likes things a little more toward just so.
Depending on your eyesight and manual skills and dexterity, HO is very popular, a good size, and a lot is available for both building and just setting on the tracks. N scale is tinier, but you get a lot more mileage bang for the buck in a given space. Availability has never been better, but it is still not the same as HO. Upwards of HO slightly is a scale growing in popularity, and that is S scale.
There are others, and I won't go on about them, but it would be a mistake for any of us to tell you to "go HO", or "try N scale." This is a key decision that one must make from a sound basis in understanding. So, seeing is believing, and if you can get to a hobby shop to hold and view items in the various scales you would serve yourself well and wisely.
Play with various track configurations. The short sections with the plastic ballast affixed to the rails is very costly, and it limits what you can do in the way of track laying, but it is all good quality, generally, and fun to play with. Most of us use flextrack because of its 'flexible' nature in allowing us to tailor our track layout to the space and its configuration.
I won't say more just yet, but would like to encourage you to continue to be open-minded, patient, and to continue to read tons before you slap your plastic down on the counter.
-Crandell
