There are three main tools of scientific investigation that help in understanding the behavior of a physical system. They are theory, experiments and computer simulations. In theory, we develop mathematical equations to describe the phenomenon and try to solve them using analytical techniques. In experiments, we monitor the physical phenomenon by actually performing it and explain it. Computer simulations are like virtual experiments where we model the phenomenon with the help of a computer and monitor it. This method helps in bringing in more complexity into the theoretical model and hence the virtual experiments will be more near to the actual physical phenomenon.