An internship is like a field trip or a sleepover where you go to a grown-up place to learn new things and try them out for yourself. Instead of going to a regular school classroom, you go to a company or organization to see how they do things.
Say you love animals and want to be a veterinarian when you grow up. You might be able to go on an internship at a vet's office. Then you get to watch the vet work, ask them questions, and even help with some of the things they do.
Internships can be good ways to learn new skills and get experience for your future job. It can also help you figure out if you really like a certain kind of work or not. Some internships might even pay you a little bit of money or give you school credit for what you learn.
Overall, internships are kind of like practice jobs for kids who want to learn about different careers.