Well, when you go to the doctor, they might give you something called a prescription. A prescription is like a special note that tells someone at a pharmacy what kind of medicine you need to help you feel better.
The doctor will write down the name of the medicine and how much you should take. They might even draw little pictures to show you how to use it. When you take the prescription to the pharmacy, the person there will read it and give you the right medicine.
On the other hand, a description is like a little story or explanation that someone might use to describe something. For example, let's say you got to see something really cool like a rainbow. Someone might ask you what it looked like, and you would give them a description. You might say that it was a big arch of colors in the sky, and that it was really pretty.
So, a prescription is something that helps you get better when you're sick, and a description is something you use to explain or talk about something you've seen or experienced.