The main feature of Quantum Computing that differentiates it from classical computing is the use of quantum bits or qubits. Unlike standard bits that represent either 0 or 1, qubits can exist in a state of superposition, allowing them to represent multiple values simultaneously. This capability enables quantum computers to perform complex calculations at unprecedented speeds, fundamentally changing how certain problems are approached, such as cryptography and optimization. The principles of quantum entanglement and superposition are key to expanding computational power exponentially.