Hard Drive (HDD)/SSD
A hard drive, also known as HDD is an older style of storage technology, its is called Hard Disc Drive. Hard drives hold documents, videos and applications. Which has moving objects inside, a disc and an arm, now-a-days we use the SSD, Solid State Drive do not have moving objects inside, this makes the SSD faster and doesnt break if you drop your computer the SSD does not break as easily. It doesnt stores as much information as the hard drive does because it isnt as developed as the hard drive. Over the years the hard drive have been developed and been taken a huge amount of time to store as much space as possible.
Optical drives are for playing optical drives, they play CD's, DVD's and Blu-Ray Discs. They store softwear, and you can play a movie. Now-a-days the mac book air pro is far too thin for that ( optical drive shown below) with apple software they use the internet soo you have too go on to the internet and download it from there.
Monitors are the sceen that is projecting what is doing at the back of the computer