This document introduces numerical methods and their importance in computer science and engineering. It explains that numerical methods are used to approximate solutions to mathematical problems that cannot be solved analytically or that are too computationally expensive to solve analytically. It outlines the typical steps involved in using numerical methods which are to formulate a mathematical model, construct an appropriate numerical method, implement the method, and validate the solution. Finally, it provides some examples of how numerical methods are applied in fields like engineering, science, and modeling real-world phenomena.