Input devices allow a user to enter data, information and instructions into a computer. The most common example of this is a keyboard. Other devices like mouses, microphones, cameras and scanners are also input devices.
Output Devices
An output device allows you to get data and information out of a computer. An example of an output device is a monitor, something most computers have. Two other common examples are printers and speakers.
Storage Devices
A storage device 'stores' data and instructions for anywhere, even permanently if you want it so. All personal computers have memory devices and most have hard-disk storage as a storage device. Other common examples are USB sticks or CD/DVD's.