Authentication is the process of verifying that a person is indeed who they claim to be.
Biometric authentication refers to using a physiological characteristic to perform that verification. Biometrics offer some security advantages over other authentication methods, for example an eye cannot be stolen like a key card or forgotten like a PIN or a password, and biometrics cannot be shared between individuals. At the time of enrollment, documents or other means are used to identify the individual, and the biometric measure is captured and stored for future comparison. In order for a biometric measure to be useful for authentication, it must be unique to the individual, remain constant over the life of the individual, and be readily available. Biometrics that meet these requirements include fingerprints or finger scans, retinal scans and iris scans.