Okay kiddo, so imagine you have lots and lots of toy cars, and you want to keep them all safe and together in one place. You get a big box with lots of little spaces inside where you can put each car, and you can close the box to keep them safe.
A disk enclosure is kind of like that box, but for computer parts instead of toy cars. Inside your computer, you have a hard drive that stores all your important files and programs. But sometimes you need more space or a backup in case something goes wrong.
So you get a disk enclosure, which is a special box that you can plug your hard drive into. It has a plug that goes into your computer like a USB or Thunderbolt cord, so your computer can access the files on the hard drive. The enclosure also has its own power supply, so the hard drive can run even when it's not inside your computer.
This means you can take your hard drive out of your computer and put it into the enclosure to keep it safe, or even take it with you somewhere else if you need to. It's a bit like a portable safe for your important computer stuff.
Does that make sense?