The "all around" to the technology. Also called Case. Consisting of different materials. Available in different sizes and designs. Is necessary to keep together the technology such as motherboard, drive, hard drives, graphics cards, etc. and shoot.
However, the smaller the case, the smaller the technology involved. That's why not every case fits every technique.
Meanwhile, there are many followers of the so-called "case modding". That The computer cases are modified and rebuilt in the most creative way to create the most unique case possible.