Superposition is a fundamental concept in quantum mechanics where a quantum particle, such as an electron or a photon, can exist in multiple states simultaneously. In quantum computing, this means that quantum bits (qubits) can represent both 0 and 1 at the same time, unlike classical bits which are either 0 or 1. This property allows quantum computers to process a vast number of possibilities in parallel, greatly increasing their computational power for certain tasks. Superposition is key to the potential speed and efficiency advantages of quantum computing over traditional computers.