JTAG, or Joint Test Action Group, is a standard for testing and debugging electronic devices. It allows engineers to access and control the internal functions of a chip or circuit board through a dedicated interface. This is particularly useful for identifying faults and verifying the performance of hardware during development. The JTAG interface typically consists of a few pins on a device that connect to a debugger or programmer. By using JTAG, developers can perform tasks such as programming firmware, running tests, and even diagnosing issues without needing to physically access the device's internal components.