Imagine you have a toy car that you really love playing with. You want to share it with your friends so they can play with it too, but your mom says you can only share it if your friends promise to give it back to you when they're done, and they can't break it or paint it a different color without your permission.
This is kind of like the free software definition. When people create computer programs, they can choose to let other people use and share them in different ways. The free software definition says that people should be able to:
1. Run the program for any purpose
2. Study how the program works and change it to suit their needs
3. Redistribute copies so they can help other people
4. Distribute modified versions, so they can help others even further
Just like your toy car, people can use free software as long as they promise to follow certain rules. These rules are called "licenses," and they explain exactly how people can use and share the software.
The free software definition is important because it helps promote collaboration and innovation. When people are free to share and improve programs, they can work together to create better software that helps everyone.