Tires are the most important element in the quest to get a car to handle well.
That's why they're the first to be discussed. Tires are 90% of a car's set-up, any time, anywhere. They're the first thing you should focus on, the first thing to get right, before you even start thinking about anything else.
No other adjustment can compensate for bad tires; if you make a bad choice, you're basically screwed.
Your tires are the only link between the car and the ground. That link depends solely on the friction between the surface and the tire's contact patch, so let's have a look at how friction works first.