Biometrics is the science of identifying or verifying the identity of a person based on physiological or behavioral characteristics. Physiological characteristics include fingerprints, retinal pattern, iris, and facial appearance. Behavioral characteristics are actions carried out by a person in a unique way. They include signatures, voiceprints, and gait, although these are naturally dependent on physical characteristics as well.
Biometrics have several advantages over conventional password and PIN based systems. First, a biometric does not need to be remembered and cannot be easily lost. This makes it much easier for the user. Furthermore, a biometric can not be easily stolen or loaned to a friend. This makes it more secure from a system point of view. Moreover, a biometric typically has a higher information content than a password thus making it harder for a hacker to crack such a system using brute force.