Hello Shrirish,

Mechatronics is the combination of mechanics and electronics field of engineering. It also involves software aspect. Whereas robotics is the branch of study that deals with the construction and design of robots or robotic machines. So basically mechatronics is the theoretical understanding and foundation for robotics which is its application. Robotics is a subdivision is mechatronics.

Theory of Machines, Thermodynamics , Hydraulics and Pneumatics, CAD/CAM, manufacturing processes, digital electronics, linear Integrated circuits,analog electronics and computer programming are main topics under mechatronics

Artificial intelligence, robotic motion science, machine learning, computer progamming for robots ,designing etc are topics under robotics.

You can always research and know more about these topics by going through a college's syllabus . You will get better idea.

Hope this helped

All the best