Quantum superposition is a fundamental principle of quantum mechanics that allows particles, like electrons, to exist in multiple states at once. Instead of being in one specific position or state, a particle can be in a combination of all possible states simultaneously until it is measured. This means that the particle's properties, such as its location or energy, are not determined until an observation is made. This concept is famously illustrated by the thought experiment known as Schrödinger's cat, where a cat in a box is both alive and dead until someone opens the box to check. Quantum superposition challenges our classical understanding of reality, suggesting that at the quantum level, things can be much more complex and interconnected than they appear.