A hard drive is the part of your computer which permanently holds or stores your personal, operating system and program files. They come in different speeds, sizes and types. They sometimes fail and when that happens, the data on them may be lost unless you have backed up the data previously.
One way to back up the data is to use old hard drives from retired computers or deceased computers. Using an external drive interface, I connect them to whatever computer I wish via the USB port. Then the files and folders can be copied to the hard drive. Being a computer professional, I have many old hard drives in my inventory so this isn’t a big deal. If you don’t have extra hard drives laying around, you can buy external hard rives with built-in enclosures ready to connect to your computers.