Biometrics refers to the automatic identification of a person based on their physiological characteristics such as fingerprints, face recognition, DNA, palm prints, retina, and voice recognition. It provides identification through measurable biological characteristics. Some common biometric technologies include fingerprints, iris recognition, hand geometry, retina scans, facial recognition and voice identification. While biometrics provide secure identification without keys, cards or passwords, they have disadvantages such as identical twins may match for some biometrics and voices or retinas can change over time.