Biometrics is the method of automatic identification of an individual by using their certain measurable physiological or behavioral characteristics like fingerprints, palm prints, hand geometry, iris, retinas, faces, hand veins, facial expressions, signatures, and voiceprints. Biometrics has overcome the problems of traditional verification methods like cards, tokens and Password or PINs. Biometric indicators have an edge over traditional security methods in that these attributes cannot be easily forgotten, stolen or shared; personally they have to go through the system. This paper reviews all biometrics and their various studies that have explored the technical and convenience issues and comparison between all the biometrics with an objective to provide insights on their reliability, performance, security, convenience and acceptance.