A qubit is a quantum bit, a unit of information that can exist in more than one state simultaneously. Unlike a classical bit, a qubit can be in multiple states at the same time and can be manipulated and measured as if it were a single entity.
This makes qubits incredibly powerful for quantum computing, as they can perform several calculations at once. However, this also makes them very delicate, as any outside influence could cause the qubits to collapse into a single state.
Qubits are usually made from materials like photons or atoms, which are carefully isolated from their surroundings. This allows them to remain in multiple states for long periods of time without being influenced by outside forces.