Face detection technology uses computer vision and biometrics to automatically detect and identify human faces. It works by capturing a digital image, detecting and extracting a face, measuring nodal points like eye and mouth positions, and comparing these measurements to a stored database to identify the person. There are two main applications - verification like mobile face unlock, which does a one-to-one comparison, and identification like airport security, which does a one-to-many search of a database. The key purpose of face detection is for security and privacy by uniquely identifying individuals.