Quantum states are fundamental concepts in quantum mechanics that describe the unique state of a quantum system. They encapsulate all the information about a system, such as its position, momentum, and spin. A quantum state can exist in multiple configurations simultaneously, a phenomenon known as superposition, which is a key feature distinguishing quantum systems from classical ones. When a measurement is made, the quantum state collapses to a definite value, revealing one of the possible outcomes. This behavior is often illustrated through thought experiments like Schrödinger's Cat, which highlights the strange and counterintuitive nature of quantum mechanics, where particles can exist in multiple states until observed.