Quantum mechanics is a fundamental theory in physics that describes the physical properties of nature at the scale of atoms and subatomic particles. It quantizes energy and matter, proposing that energy transfer and particle behavior are not continuous but occur in discrete packets, or quanta. Central concepts include wave-particle duality, which suggests that quantum entities can exhibit properties of both waves and particles, and the uncertainty principle, which establishes a limit on the precision with which certain pairs of physical properties can be simultaneously known. The theory is crucial for understanding the behavior of electrons in atoms, the operation of lasers, and the principles governing chemical bonding and radioactivity, forming the basis for modern technologies like semiconductors.