HDD and SSD
HDD stands for Hard Disk Drive. It is used in computers and stores all of the photos, work and games, etc, which is on your computer. It is made up of a spinning disk and an arm, a bit like a record player. When you save something on your computer the arm prints/draws the file onto the disk and saves it, similar to when the needle on a record player touches the recored, it plays the song. The HDD is used in Computers and thick laptops, it's definitely not able to fit in the new laptop the MacBook Air.
SSD stands for Solid State Drive. The SSD is very much the same as the HDD but the SSD is a lot thinner, faster and just generally a lot better. Even though it is better, the price is a lot higher and more expensive than the HDD. But it can fit in iPads and very thin laptops.
This is what the disk inside of the HDD looks like.
This is what the inside of an SSD looks like.
An HDD would not be able to fit inside an iPad, but an SSD would, as it is thinner.
An Optical Drive is what you would find in a laptop, computer or a DVD player which you put your disk into to be displayed on the screen. CDs, Blu-rays and DVDs are the common disks you would put in an Optical Drive.
The Optical Drive simply scans the disk you place in and plays it on the screen of your TV, laptop or computer.
Laptop Optical Drive
This is where you would find an Optical Drive in a laptop and what it would look like.
DVD player Optical Drive
This is a DVD player showing the disk inside the Optical Drive.
Blu-Ray DVD Player
This is a Blue-Ray DVD player.
A CPU stands for Central Processing Unit. It simply carries out the instructions in the computer and downloads things from its memory. CPU is measured in GHz.
It is a bit like our own brains, for example whenever we want to walk, our brain takes a few calculations and then we can walk. Whenever we save something on our computer, the CPU saves it in the same way our brain makes us walk.