Definition: Quantum mechanics is a branch of physics that deals with the behavior of particles at extremely small scales such as atoms, subatomic particles. It provides a framework for understanding how these tiny objects behave in ways that classical mechanics cannot. The key concepts of quantum mechanics include the concept of "quantization," which refers to the breaking down of classical laws into discrete parts or "quantities." This allows us to describe the behavior of particles with greater precision than is possible using only classical physics. For example, it can be used to explain many aspects of the behavior of subatomic particles, such as their motion and interactions. Quantum mechanics also introduces new concepts such as superposition and entanglement. Superposition refers to a property where particles are able to exist in multiple states at once. Entanglement is another phenomenon that allows quantum systems to be correlated in ways that classical systems cannot. These concepts have profound implications for our understanding of the universe. Quantum mechanics has had a major impact on our understanding of the world, and it continues to evolve with new discoveries and theories being developed every day.