@pubert224: Quantum refers to the smallest possible unit of any physical property, often related to energy in the context of quantum mechanics. Quantum mechanics is the branch of physics that deals with the behavior of particles on the smallest scales, such as atoms and subatomic particles. It fundamentally challenges our classical understanding of nature, introducing concepts like wave-particle duality (where particles can behave as both particles and waves), superposition (where a particle can exist in multiple states at once), and entanglement (where particles can instantaneously affect each other regardless of distance). Quantum theory explains the behavior of matter and energy at the smallest scales and forms the basis for technologies like semiconductors and quantum computing.