Computer simulation is like a video game that helps us understand how something works. It gives us a chance to play around with different ideas, and figure out what will work best. It's like a virtual world with its own rules, and we use it to try and solve real world problems. We can even build models that match things in the real world. For example, a simulation can help us understand the movement of water or traffic in a city. We can then use that simulation to help us plan things out and make decisions about what will work best for us.