A quantum computer differs from a classical computer primarily in its computational capabilities and architecture. While classical computers process information in binary bits (0s and 1s), quantum computers use qubits, which can exist in multiple states simultaneously due to superposition. This allows quantum computers to handle complex calculations at unprecedented speeds. Quantum entanglement further enhances their problem-solving capabilities, enabling solutions to problems less feasible or impossible for classical computers. Consequently, quantum computing has the potential to revolutionize fields such as cryptography, optimization, and drug discovery.