Supercomputers are the most expensive and the fastest kinds of computers. They can perform superior calculations and intensive tasks. Mechanics, quantum physics, molecular theory, and weather forecasting are best studied by means of supercomputers. Their well-designed memory hierarchy and their ability to process parallel things give the computers greater transaction processing powers. A typical supercomputer can do up to a trillion or more individual calculations every second.
Server computers are at a lower level as compared to supercomputers. They try to solve complex problems, but do not focus on single problems alone. An instance of server computers would be those that Wikipedia stores its encyclopaedia on. These computers go and search the pages that you are looking for. However, it becomes a job for a server when the computers have to go and find lots of people and send them to the right place. They are usually large in size and they have many hard drives and large processors. Running on them are the programs that allocate resources and serve client requests. They are designed to be resistant to crash and fail safe. A server is a central computer, which comprises lots of programs and data.
A personal computer is also known as a microcomputer or a PC. The capabilities of a personal computer have changed greatly ever since electronic computers were introduced. The introduction of a single-chip microprocessor with all the circuitry in it became highly popular. Early personal computers were sold in the forms of kits and in limited volumes. Home computers were developed for personal use in the 1970s and the 1980s. They offered some personal productivity. Today, a personal computer is an all-round device that can be a media server, a productivity tool, as well as a gaming machine.
Not only are workstations expensive, but also high end. They are named improperly sometimes for marketing reasons. Earlier, real workstations were never sold at retail stores, but now this is changing gradually.