Recent research on iris is not only on recognition; emerging trends are also in medical diagnostics, personality identification. The iris based recognition system rely on patterns/textures present in the iris, the color of the iris, visible features present in the iris, geometric features of the iris and the SIFT features. An overview of biometric generation is presented. Human iris can be viewed as a multilayered structure in its anterior view. The iris consists of three zones, the pupillary zone, collarette and the ciliary zone. The texture features present in the pupillary zone and collarette are used for identification. As these features are closer to the pupil they are not affected by the occlusion caused by eyelid or eyelashes. The geometric features of the iris can also be used for human identification. The structure of the iris is more related to the geometric shape and hence the extraction of these features is also possible. An overview of the performance metrics to evaluate a biometric system is also presented.