Desktop computers are probably the type of computer you are most familiar with. They come with a monitor (now usually a TFT screen), keyboard, mouse, CD-RW and a DVD-RW or at least a DVD-ROM.
Laptop computers are also very common. They are usually have the same processors as desktops and similar sized main memory and hard disk drive although you will pay more for a laptop as a desktop with the same specification. Laptops have the advantage that they can carried about easily and run from a battery.
Often they have built in wireless technology allowing them to connected to network without having to use cables. Laptops do not come with a mouse due to the fact that they are often used where there in not a table to use a mouse on. Instead they have a touchpad built into them. You would also expect a laptop to have a CD-RW and DVD-ROM as standard.
Palmtop computers (sometimes called PDAs (Personal Digital Assistants)) have a small touch sensitive screen and come with a stylus allowing the user to select things off screen. Data entry is usually done using handwriting recognition although some PDAs do have a small keyboard.
They can be used to do tasks similar to ones done by desktop and laptops but more often they are used for note taking, calendars, address books and a means of sending and receiving email. A palmtop works together with a desktop or laptop so data can be transferred between computers. This is done using a cable or using Bluetooth wireless technology.
Mainframe computers are very large powerful computer systems that are usually at the heart of a business. The mainframe computer will have a very powerful processor, large amounts of main memory and a huge backing storage capacity.
They are accessed through one or more terminals. Terminals consist of a screen, keyboard, mouse but no processor as all the processing is done by the mainframe.
Here’s a little video to show you the types of computers