A NAND gate is a fundamental digital logic gate that produces an output which is false only when all its inputs are true. It combines the functions of an AND gate and a NOT gate. In simpler terms, if you input true (1) into both inputs, the output will be false (0). For any other combination of inputs, the output will be true (1). NAND gates are widely used in electronic circuits and are essential for building more complex logic circuits. They are considered universal gates because you can create any other logic gate, such as OR or AND, using just NAND gates. This versatility makes them crucial in digital electronics.