A quantum computer operates on the principles of quantum mechanics, allowing it to process information at speeds far beyond traditional computers. It uses qubits instead of binary bits, enabling superposition where qubits can exist in multiple states simultaneously. This allows quantum computers to explore multiple solutions simultaneously, leading to faster problem-solving capabilities. Quantum computers also utilize entanglement, where the state of one qubit can affect another regardless of distance, enhancing computational power. The physical appearance of a quantum computer is vastly different from a regular computer, resembling complex machinery with a network of wires and components, creating a sci-fi-like environment.