A nice hairpin curve here, or a sweeping chicane there. If your not doing multi lanes then you just have additional options for creating different corners as you wish. You can refer to the featured image on this page to see this concept displayed. Radius 1 is the tightest of the corners and continues going out through radius 4. While the straight track components will be the same for any lane, you will need different radius curves to line up next to other lanes. These are useful if you are creating a multi lane track.
Some radiuses offer multiple track components. Scalextric offers four different curve radiuses.
If your looking to follow a specific track layout plan that you have found here on Slot Track Pro or one you have designed yourself, you will want to learn about the specific track pieces. Track packs consisting of hairpin turns, jumps, side swipe sections, and regular old straights and corners. Scalextric offers Track Extension Packs consisting of specific track parts and pieces. It is super easy and simple to expand upon any track that came with your slot car set. Scalextric Track can be configured to create the wildest slot car track you can dream of or reproduce any number of famous real world racing circuits.