There are many ways of categorizing the different kinds of computers. The first categorization is on the basis of how these computers operate.
Analog computers works on an input of values. These values vary continuously and therefore the best result of an analog computer is only an approximation. They never receive stable values. Their input values are physical quantities like voltage and so on.
Digital computers work on numerical values. These values are 0 or 1 and each of them is called a bit. Of all kinds of computers, digital computers are faster and give more accurate results. They have only two levels-one for input and another for output. Digital computers themselves are of two types. You can either have a special purpose digital computer that is built to run a specific application or you can have a general purpose digital computer which can be used to run a variety of applications.
Hybrid Computers take the best of both worlds-digital and analog. Today you can easily find a digital to analog convertor and also vice versa. A common example of their usage is in the hospitals where such conversions are important and desired.
The next type of categorization of the kinds of computers is one the basis of how they are configured. All computers in this category are digital computers.
Let us start with the most expensive of all kinds of computers, the super computer. It is the most accurate, the fastest and certainly, the costliest. Usually, they are used for functions that require too many numerical calculations non stop as they can process billions of values at the same time. They are used in simulation, dynamics, energy reactors and high sounding things like that.
Mainframe computers are a step lower than super computers. If super computers can process billions of instructions and/or values, then mainframe can process thousands. This also means that they are also kind of expensive. They are used in bookings in railway departments and air travels.
Mini computers come after mainframe computers. They are slower than mainframe computers and have a lower storage capacity than them. Also some key functions and features of the mainframe computer might be unavailable in a mini computer. They are more affordable.
Microcomputers were built after the invention of the microprocessor chip. This made these kinds of computers much more affordable. They are of three kinds. Firstly we have Desktop computers. They are easy to use and economical. They are also called personal computers. They are best suited for individual usage. Secondly, we have laptop computers. These kinds of computers are portable. They are also called notebooks. They weigh less and are thinner. You can fold the screen when the laptop is switched off. Lastly, we have the handheld computer. It is also called PDA or Personal Digital Assistant. They power source is a battery and are operated through a pen. They are touch screen and have very limited abilities like making appointments, playing games and so on.