Biometrics uses physiological characteristics like fingerprints, iris patterns, and voice to identify individuals. The iris, located around the pupil, regulates the size of the pupil and has complex random patterns that are unique to each person. Iris recognition uses cameras to capture an iris image, overlay a grid to analyze patterns, and compare it to stored templates to identify a person. Iris scanning is highly accurate for identification and authentication purposes across applications like border control, computer login, and financial transactions due to the iris having unique patterns that remain stable throughout life.