The document discusses the four main types of computers:
1) Microcomputers, which include personal computers (PCs) designed for individuals, as well as portable computers like laptops and tablets.
2) Minicomputers, which are mid-sized multi-user systems that can support 4-200 users simultaneously.
3) Mainframe computers, which are very large and expensive systems capable of supporting hundreds or thousands of users simultaneously.
4) Supercomputers, which are the fastest type of computer used for specialized applications requiring immense calculation like weather forecasting.