Track Camera and Track Motion

[MahaB82A]

If all are in motion which one to select. I mean for example consider  a drone takes a video of sea where sea, boat on the sea & drone camera is in motion.

[RobShultz]

If I'm understanding your question correctly I  would try track motion and then using the point tracker to track one item on your screen.

[Rick Gerard]

Camera Tracker requires a good amount of fixed geometry in the shot. A drone shot of a boat on the ocean will not work. 

My recommendation would be to use Mocha AE to track the boat. That will give you position rotation, scale, and even shear, even corner pin (perspective) data that can be used to attach just about anything to the boat. The After Effects tracker might also work. It tracks a feature. A feature is a group of pixels with sufficient detail for the pattern to be recognized as it moves in the frame. More than one feature must be tracked if you need position, rotation, and scale information.  

The User Guide has a couple of tutorials that use tracking. 

[MahaB82A]

In this video both camera and object is moving but to track the motion of the car "Track Motion" is used.