A full subtractor is a logic circuit that performs subtraction between two binary digits. It has three inputs - the minuend, subtrahend, and a borrow bit. It uses logic gates like OR, XOR, and NAND gates. A full subtractor is made up of two half subtractors and can subtract two bits while accounting for a borrow from the next higher order bits. It has three inputs and two outputs - the difference and a new borrow bit. Full subtractors are used in arithmetic logic units of computers and other digital devices to perform subtraction operations.