Quantum superposition is a fundamental concept in quantum mechanics that allows particles to exist in multiple states simultaneously. This means that a particle can be both in a state of 'up' and 'down' or 'spin up' and 'spin down' at the same time. This might sound counterintuitive based on our everyday experiences, where objects have definite properties. However, at the quantum level, particles behave differently, and their properties are described by wavefunctions.

One of the famous examples illustrating quantum superposition is the thought experiment of Schrödinger's cat. Imagine a cat inside a closed box with a radioactive substance that may or may not decay, triggering the release of poison gas. According to quantum mechanics, until we open the box and observe the cat, it can be considered to be both alive and dead simultaneously, in a superposition of states.

Measurement plays a crucial role in quantum mechanics. When we make a measurement on a particle in a superposition of states, the wavefunction collapses, and the particle is forced to take on a definite value. This is known as the measurement postulate. In the case of Schrödinger's cat, observing the cat would cause the wavefunction to collapse, resulting in the cat being either alive or dead, but not both.

The concept of quantum superposition has been experimentally confirmed through various experiments, such as the double-slit experiment. In this experiment, particles like electrons exhibit interference patterns when passing through two slits, indicating the presence of multiple possible paths. Without superposition, we would not observe such interference patterns.