Question

What is quantum mechanics?How does it work?

Answer 1

Quantum mechanic or wave mechanics deals with the wave nature of matter. Here instead of particle as in mechanics we deal with a wave of probability.
Example:- The Schroedinger's equation in wave mechanics is an equivalent form of Newton's law un mechanics.

Answer 2

it's the physics that explains how everything works: the best description we have of the nature of the particles that make up matter and the forces with which they interact. Quantum physics underlies how atoms work, and so why chemistry and biology work as they do.