Computers use output devices to convey information to a user. Three commonly used output devices are a printer, a monitor, and speakers.
Aside from output devices, computer hardware components include input devices, a system unit, storage devices, and communications devices.
An input device is any hardware component that allows a user to enter data and instructions into a computer. Six commonly used input devices are the keyboard, mouse, microphone, scanner, digital camera, and PC camera.
The system unit is a box-like case made from metal or plastic that protects the internal electronic components of the computer from damage. The system unit contains the central processing unit and memory. The central processing unit (CPU) is the electronic device that interprets and carries out the basic instructions that operate the computer. Memory is a temporary holding place for data and instructions.
A storage device records and retrieves data to and from a storage medium. Six common storage devices are a floppy disk drive, a Zip® drive, a hard disk drive, a CD-ROM drive, a CD-RW drive, a DVD-ROM drive, and a DVD+RW drive.
A communications device enables computer users to communicate and exchange items such as data, instructions, and information with another computer. A modem is a communications device that enables computers to communicate usually via telephone lines or cable.
For more info, here's a broad survey of concepts and terminology related to computers from UWF.edu.