There are three points in every corner. These are called the Turn-in, Apex, and Track-out.

Turn-in
This is the point at the end of a straightaway where you begin to turn. Though it sound very simple and rudimentary, the Turn-in is crucial to a successful turn. Your Turn-in sets up your car in the corner, and largely determines where your Apex and Track-out points will be.

The Turn-in is defined by both when you turn in and how much you turn in. If you turn-in too early or too late, your Apex will be off and your Track-out point will be either sub-optimal or disastrous (See Common Mistakes for more on this). Likewise, if you turn in too much or too little, your Apex and Track-out point will suffer the same fate.


Apex
This is the inner-most point of your turn. In a classic 90 degree corner, this is the point where you will touch the inside edge of the track (see The Line, Part 1: The Basics for more on this).

The Apex is largely determined by the Turn-in point. If you turn-in early, you will hit the Apex early. If you turn-in late, you will hit the Apex late.

A driver’s primary point of focus in a turn should be the Apex, as where you Apex plays a huge role in determining your Line through a corner. Once the Turn-in point is reached, you need to fine tune your inputs to ensure that your Line brings you to the proper Apex.

Track-out
This is the point where you straighten the wheel after you have finished the corner. In a classic 90 degree corner, it is the point on the outside edge of the track.

The optimal Track-out point is based primarily upon the location of the Apex. Its affect on Track-out will be discussed below. Your Track-out point is crucial because it is the point at which you enter the next straight. You want to hit the correct Track-out point because doing so allows you to carry the most speed onto the straightaway. More speed at the start of a straight equals more speed at then end of a straight, and we always want more speed.

How are the Turn-in, Apex, and Track-out Connected?
In short, your Turn-in affects where you Apex, which affects where you Track-out. The Apex acts like a central “pivot” for your Line, and where you Apex plays the largest role in how fast your Line through a corner will be. Your Turn-in point should therefore ALWAYS be the point that allows you to hit the correct Apex consistently.

How Changing Your Apex Changes Your Line
If you Apex too late, your Track-out point will be much farther up the straight. In some cases, if you Apex very late, you may not even need to track all the way to the edge of the track. This is undesirable as it means you are not using as much of the track as you could. And that means that you are not going as fast as you could. And nobody likes going slow.

If you Apex too early, then you are in serious trouble. Apexing too early moves your Track-out point farther back. If you Apex early enough, you can actually track out before you have finished turning. If you were going slower than your limit, great! You left yourself room to recover. If you were pushing hard, you have now set yourself up on a line that takes you completely off of the course! This is why you should err on the side of apexing late rather than early.