Quantum mechanics is a branch of physics that deals with the behavior and properties of matter and energy on the atomic and subatomic scale. The quantum world is governed by the laws of quantum mechanics. These laws are completely different from those of classical physics.
It's a world where particles can exist in more than one place at the same time, until they are observed or measured, where light can behave like a particle or a wave, and where space and time are not absolute but depend on how we measure them.
