The 3D Camera Tracker in Adobe After Effects is a powerful tool that lets you analyse your footage and extract information about the movement of the real life camera used to film the scene. Assuming the tracking data is spot on, you can then place other visual elements in the 3D space of your scene and they will follow the movement of the camera correctly.
If you look at the actual frame you will see that it is rather blurry and there are very few features for the 3D Camera Tracker to latch on to. Again, this is hard to fix afterwards, but can be avoided if you plan out how to shoot your footage.
I hope this tutorial gave you a solid overview of the 3D Camera Tracker in Adobe After Effects and showed you how to resolve some of the common problems that you may encounter when tracking your footage.