Basic components of a computer
The processor is that part of the computer that does all the work of computation. It does this in collaboration with the computer's main memory where live data is kept and fetched by the processor for processing. A processor is distinguished by its speed measured in Gigahertz (GHz). The higher the speed, the faster the PC.
Main Memory stores live data and loses it once the power source is turned off. The processor fetches instructions or data from main memory to process. Generally, the more Random Access Memory (RAM) you have, the better the PC will run when using several programs at once. A typical office PC can run well with 512 megabytes (512MB) of memory and this is a good minimum specification.
The hard disk is used to store the data that you create. This may be your business data or data on class work for students or games. It has a larger capacity than the RAM. A typical office computer has about 40 gigabytes (40GB) of hard disk space. Larger data stores may require a larger capacity hard disk. Where that storage serves the purposes of sevral users in a network, the disk may be used to service those needs of users and may be set up as a Server. The file server (with accompanying software) may be mounted in a separate (dedicated) PC.
The monitor is the display screen. There are two types of monitor - flat screen or cathode ray tube. Flat screens are more expensive but are becoming more widely used as they use less desk space and generate less heat. Select at least a 17 inch monitor for desktop use.
The keyboard and mouse usually come as part of a bundle. They may come as connected (wired to the PC using a cable) or as a wireless device. The wireless devices make desktops neater.