Biometric systems are computer-assisted identity recognition systems that can identify people by assessing their physical and biological characteristics. With the help of this technology, the processes that require confidentiality are performed without errors, without unauthorized copying and without the need for another person to control the access, because the physical characteristics that are taken into consideration during the identity recognition process are different in each person. Fingerprint recognition, hand geometry recognition, palm recognition, iris/retina recognition, face recognition, voice analysis, signature analysis are among the most common methods for recognition purposes. Each of these systems have advantages as well as some drawbacks when the sectors in which they are going to provide services are considered. The convenience of a system is determined with the assessment of some factors such as its price, error rate, sensitivity level to the environment and being user-friendly. After the continuous researches, these methods have been optimized with the developing technology day by day, and the costs have been reduced.