Peripherals are secondary computer devices. They are tools such as a printer, keyboard, or mouse, that are not part of the essential computer but contribute to its functionality. Although not technically part of the main computer, many peripherals are essential in using your computer efficiently and effectively. For example, everyday tools such as a monitor, keyboard, and mouse, although seemingly standard, are considered peripherals.
There are two types of peripherals. External peripherals, and internal peripherals. External peripherals are tools such as the mouse, keyboard, monitor, external zip drive or scanner. Internal peripherals, also reffered to as integrated peripherals, can be tools such as an Optical Drive, CD-ROM drive, CD-R drive or external modem.
Peripherals must be somehow, either internally or externally, attached to the computer. This can be done in the traditional way with wires and chords, or more recently, wirelessly. Many peripherals are now equipped with wireless connectivity. Examples of such peripherals are a wireless keyboard, mouse, or speakers. Wireless peripheral connections offer great practicality and are increasingly a standard part of the everyday person's computer set-up.
Although some peripherals have existed for long periods of time, others are supprisingly recent inventions. For example the compact disk (CD), was invented back in 1965, while the first touch screen monitors were invented as recently as 2007. In actuality even 1965 is not so long ago. Peripherals and even computers in general are a very new aspect of technology which has developed very quickly. Computer technology has develped incredibly over a short period of time and allows us many useful tools, hopefully this growth will continue.
Sources:
1) http://it.toolbox.com/wiki/index.php/Wireless_Periph
2) http://www.webopedia.com/TERM/P/peripheral_device.htmleral
3) http://inventors.about.com/library/inventors/blcomputer_peripherals.htm