A sandbox is like a special playground for a computer program. Just like when you go to a playground, you can only play in the sandbox and not go outside of it. A sandbox for a computer program is a safe place that lets the program play around without touching the other important stuff on the computer.
When a computer program runs inside a sandbox, it can't mess with anything else on the computer. This helps keep the computer safe from dangerous programs that might want to do bad things like steal information or break things.
Think of it like a kid wearing a helmet and elbow pads when they ride a bike. The helmet and pads protect them from getting hurt if they fall off the bike. The sandbox helps protect the computer from getting hurt by bad programs.
So, a sandbox is a safe place for programs to play without causing any harm to the computer. It's like a playground with soft edges and boundaries that keep the program from wandering into the wrong place.