Today, observation, theoretical study and numerical simulation are the three most important tools that we have to explore the unknown world. Though they each have their specific strong points, they also each have certain disadvantages. The best way for us to apply these techniques in our study is to have a better understanding of these methods and make good use of them according to their properties. In this section, we will discuss the benefits and restrictions of these methods. From this we can have a better understanding of the role of numerical simulation in scientific study. This will also help us to use it properly by combining it with other methods to achieve the best results.