Hi Ayush,

Quantum mechanics, is physics at a microscopic scale. Quantum theory describes matter and energy at atomic and sub-atomic levels where classical physics does not apply due to wave-particle dual nature and the existence of the uncertainity principle.

It is useful for improvement in technology by developing Sensing, Secure communications, Computing technologies.

Feel free to ask doubts in the Comment Section.

I hope this information helps you.

Good Luck!