Non locality and uncertainty of the quantum theory was a matter of huge debate for a very long time. Einstein, Podolsky and Rosen introduced local realism which was more like a pre-deterministic idea. It said that the particles that are found in certain quantum states are the one which were in that state from the beginning. Later on J.Bell did an experiment and found out that the hypothesis of EPR was rather wrong. Though the idea of local realism was wrong it motivated many people to look from different perspectives. There are two major questions raised by the local realism on the quantum mechanics one is known as the locality loophole and the other one is detection loophole. In this paper I have discussed about the Bell’s inequalities and how it violates the idea of local realism, CHSH inequalities and also the efficiency required by the detectors to close the detection loophole.