There are basically two types of models - desktops and laptops. Desktops are non-portable devices with large screens and are used when you only use the computer at home or office. Laptops are ideal if you need to take your work with you from home to office or school, or on a vacation.
For general use, computers either operate using WINDOWS which is a Microsoft operating system or Apple, which is only used by Apple products. Both systems give the same results.
Most desktop units are comprised of a seperate tower, monitor, keyboard and mouse. Some, called hybrids, have no tower and the electronics are stored in a part of the monitor.
Laptops are self contained and work on electric or a built-in battery.