We live in a physical world that has physical problems. Those physical problems can be overcome by introducing analytical solutions or numerical solutions through the mathematical modeling. But, in general, problems are very complex. Therefore, it is very difficult or sometimes almost impossible to introduce analytical approach. Numerical approach is relatively simple and straightforward in solving the problems of the nature. Numerical solutions are mostly approximations to the true solutions of physical problems. They are based on numbers and very simple functions (i.e polynomials). Therefore, we are stepping in computational world. Then, numbers, simple functions, arithmetic operations, computations, computing methods, computers, error, convergence etc. are all the terms of this computational world.  

So welcome to the world of computing!