Computer cases have different sizes, but there are three case size groups. If you have a lot of space, full towers can fit extra parts like Extended Advanced Technology Extended (ATX) motherboards and water cooling systems. The most common type of building is a mid-rise one, which can easily meet the needs of most customers. Micro-ITX computer cases can be used with mini-ITX motherboards and are a good choice for start-up computers. Choose a case that can hold all of your computer's parts while also letting air in to keep it from overheating. Because no action can happen without the CPU's permission and execution as the computer's brain, it is called that. It communicates with all of the other parts of the computer. It has three parts that help the CPU run smoothly.