Newbie needing some visual guidance

Have always enjoyed trains. Putzed with HO scale decades ago. Wife and I decided to do a small model railroad, so we went N-scale on a 26" X 72" board (because we need to be somewhat mobile had to size to fit through doorways). I'm a visual learner. Familiar and comfortable working with electrical and electronic wiring and hook ups.

The problem I have is what people are describing when they say "bus" as in main power supply bus used to branch out to more specific needs. Does this make sense?

I could use a few photos or drawings to show me what that "bus" might look like under the board. Otherwise I keep envisioning a computer's internal busses.