Input and output hardware: input is information going intot he computer. Output is information coming out of the computer.
Input hardware includes: keyboard, mouse, microphone.
Output hardware includes: screen, speakers, lights.
When working inside a computer, make sure to discharge static electricity. Despite what the video says, you do not need to oil your computer. It might be worthwhile, though, to use a can of compressed air to blow out the vents from time to time and dissipate some of the dust.
Increasing available RAM is one of the surest ways to upgrade a computer. More than 8GB may not make a noticeable difference.