Mice and other Pointing devices
Other than the keyboard, mice are the most common type of input device. Nearly every computer has one, and they make navigating the screen much easier than trying to use just a keyboard. Mice usually use a ball, light, or a laser to track movement. Similar peripherals, such as a touch screen or laptop's touchpad, trackballs, graphics tablets, and even joysticks are “pointing” input devices.
Touch screens are becoming an increasingly popular pointing device, and someday may replace mice altogether. Other forms of pointing devices, such as motion controllers on the Wii game console, may also reveal the direction of input devices in the future.
Keyboards
The keyboard is the most common input device. It is almost unheard of for a computer to be without some form of keyboard, be it a full QWERTY keyboard or a smaller number pad, such as those found on a cell phone. It is possible to interact with most computers solely through the keyboard, without even a mouse, because they are usually the default input device. Touch screens may eventually overcome the keyboard as well, by providing an onscreen keyboard to save space.
Audio/Video Input.
Webcams and digital cameras can also be considered input devices. They provide visual data to the computer in the form of images and video. Some webcams can even be used as pointing devices by tracking the location of a person's hands or face. Microphones and digital musical instruments, such as midi keyboards, are audio input devices that provide the computer with audio data. Even an electric guitar, when hooked up to a computer, can be an input device.
To learn more about input devices, check out An Introduction to Hardware for Beginners: What Goes In and What Goes Out?
