Tracking allows you to keep a moving object/subject in focus. One you have placed the focus point (touched the screen over the area where you want the focus to be) the camera will start tracking the object/subject under that focus point even if there is movement.
To activate got to Menu then Camera Settings (camera icon at top), selected Touch AF then select Tracking AF.
The tracking shows up as a white border box and will track the subject/object as long as it's in view of the camera i.e. if you remain still as the action moves past. If you pan (move the camera by following the action) then the tracking will remain on the object/subject as long as it's in view.
If the camera loses focus while tracking, a red box will show and focus will be reset.
I did find that sometimes the tracking wanted to wander and track something else (in this case I used a heavy wind and flowers for this experiment). When it did I had to touch the screen to refocus.
Tracking is available in Auto Mode, Program, Aperture, Shutter, Manual and Lens Priority Mode. In Smart Mode Tracking is only available in Beauty Face, Best Face and Creative Shot. It's not available in Action Freeze.
The thing about the Tracking feature is that it will carry on tracking (while object/subject is in view) until you press the shutter button half way down. This then locks the focus in and as long as the subject/object remains on the same focal plane (distance from the camera) it will remain in focus. If the object/subject moves out of the focal plane after locking (pressing the shutter half way down) in the focus then it will be out of focus as the camera is no longer tracking it.
Annoying if you want to keep the moving object/subject in focus. So what do you do? If you want to rely on the camera's help you need to change the AF Mode to Continuous Auto Focus. You also need to keep the Tracking feature activated (Menu<Camera settings<Touch AF<Tracking AF)
Select Menu on the camera, make sure the Camera Settings is selected (top sub menu with camera icon) and scroll down to AF Mode, then select CAF (Continuous AF).
What this does is continuously refocus on the moving subject/object even when the shutter is pressed half way down.
If you don't want to use the Tracking and would rather pan and track the movement yourself, then select Touch AF under the Touch AF menu while leaving Continuous AF selected under AF Mode. Wherever you touch the screen to place focus, CAF will continuously focus on the area but will not track.
So to manually track you will need to pan (move the camera with the action) and keep the subject/object under that focus area. It doesn't matter if you move closer (don't forget what the closest focusing distance is of your lens) or further away. As long as the subject/object is under that focuses area it will remain in focus.
For the AF Area under Camera Settings you can use Multi AF and touch the screen to place the focus where you want it if you are not happy with the camera's placement. But, each time you release the shutter button and press half way again your selected focus will be lost (unless you press half way quickly). The camera will choose the focus points so you would then need to touch the screen again and place the focus where you want.
For something a little more accurate, Change the AF Area to Selection AF. Each time you release the shutter button and press down again, the area you chose to focus will remain there (the camera doesn't have control here, you do).
The downside of Tracking and Continuous AF is that it's not always fast. Lighting conditions can affect how fast the lens focuses but I found it lagging a bit behind which could mean lost shots.
Another issue I had (besides the camera crashing on me once or twice) was that the camera just wouldn't focus. It's happened a few times on my normal settings where the camera wouldn't focus. As for crashing, I had to remove the battery as the camera wouldn't turn off even when the switch was on Off. Don't know why this happened.
Personally I don't favour the Tracking feature all that much and prefer to use Continuous with Selection AF for moving objects. Panning and following the action takes some practice so play around. Anticipating where the object/subject is going to be can aid in getting a sharp shot.