Okay kiddo, have you ever heard of engineers? They're people who use science and math to design and create things. Now, medical engineering is when these engineers use their skills to make things that help people who are sick.
For example, they might make machines that help doctors see inside your body to find out if you have any problems. Or, they might design special equipment that helps people with disabilities move around better.
Medical engineers can also work on designing new medicines or ways to deliver medicine to your body. They might use computers to simulate how a medicine will work in your body before they actually test it out.
In short, medical engineering is when smart people use their skills to make things that can help keep you healthy and make you feel better when you're sick. Cool, huh?