Linked from
The 10 pages that link to Qubit, each with the reason it gives.
BitCompared with: Unlike a classical bit, a qubit can occupy a superposition of basis states.
Bell stateNarrower topic: Each Bell state describes a pair of these two-level quantum systems.
BQPBroader topic: Quantum circuits encode their computational states in qubits.
Spin-½Related: A spin-½ degree of freedom can encode the two-level state of a qubit.