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, athough 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.