A quantum gate is a fundamental building block of quantum computing, similar to classical logic gates in traditional computers. It manipulates quantum bits, or qubits, which can exist in multiple states simultaneously due to the principle of superposition. Quantum gates perform operations on these qubits, allowing for complex calculations that classical gates cannot achieve. These gates are represented mathematically by unitary matrices, ensuring that the operations are reversible. Common types of quantum gates include the Hadamard gate, which creates superposition, and the CNOT gate, which entangles qubits. Together, these gates enable quantum algorithms to solve problems more efficiently than classical methods.