Computer Hard Drives (HDD/SSD)
A HDD is a Hard Disk Drive, the HDD stores everything you save on your computer. It is made up of a moving arm which reads and writes information onto a disk below. They are quite big and genrally make a computer quite big.
A SSD is a Solid State Drive, it does the same as a HDD but its thin and small and doesnt have a moving arm inside. As they are smaller they can fit in iPads etc... However because they are smaller they are more expensive and appliaces that jave them are generally more expensive.
This is a picture of an HDD
This is a picture of an SSD
The MacBook Air is extreamly new but really thin, so it can only hold an SSD instead of a HDD. This makes it really expensive!
As you can see where is the space for an ODD.
Here is an ODD.
Downloading From The Internet
As you can see you don't need discs just the internet.