The hard disk drive is the main and its usually largest, data storage device in a computer. The operating system, softwares and most other files are stored in the hard disk drive. (A Disk drive used to read and write to a Hard disk.)
Optical drives retrieve and store data on optical discs like CDs, DVDs mand Blu-ray discs which hold much much more information than classic portable media options like the floppy disk.
The monitor displays the video and graphics info generated by the computer through the video card. Monitors are similar to TV but its display information at a much higher resolution.
A Input Devices is a device that can be used to send data (with keyboards, mouses, micphone and webcam) into your into a computer or other computational device
A Output Devices is a device that is connected to a computer (like a monitor, speakers, printer, headphones) that sends out data in the form of Text, Sound, Video or other type of media.
Touch Screens is a display device which allows the user to interact with a computer by touching areas on the screen.