Track wiring begins with wiring a point. The wiring depends on the type of point, and particularly on whether it is live frog or dead frog, and how the point is used: whether it connects a siding, or works with another point as part of a crossing between lines, or is part of a more complex formation.
For a small layout with only one controller, and therefore one engine moving at a time, the wiring is fairly simple. A more complicated layout may have two or more controllers, and then issues arise about how the controllers are switched. Each controller may be responsible for a fixed area of the layout (area control) or may be able to drive a single train over any part of the layout (cab control).
In 2-rail wiring, the rails are electrically positive and negative. Return loops pose a particular problem in that somewhere in the loop a positive and negative rail must join. Insulating gaps and switches are required to ensure that a short circuit does not occur and that a train can be driven round the loop.