The Test Access Port (TAP) is a standardized interface used in electronic devices to facilitate testing and debugging. It allows engineers to access the internal circuitry of a device without needing physical probes. This is particularly useful for identifying faults and verifying the functionality of integrated circuits. Boundary Scan is a testing method that utilizes the TAP to check the interconnections between integrated circuits on a printed circuit board. By adding special boundary scan cells to the chips, engineers can shift test data in and out, enabling them to detect issues like shorts or opens in the connections without needing to access the pins directly.