Touch ID is a fingerprint recognition feature developed by Apple that allows users to unlock their devices and make secure purchases. It uses a capacitive sensor to capture a high-resolution image of a user's fingerprint, which is then converted into a unique mathematical representation. This technology enhances security by ensuring that only registered fingerprints can access the device. Touch ID is commonly found on various Apple products, including the iPhone and iPad, providing a convenient and quick way to authenticate identity without needing a password.