Okay kiddo, so do you know what NASA is? Yes? Great! So NASA is a group of very smart people who explore space and they built a special machine called Osiris-REx to explore a really big rock in space called an asteroid.
Now, Osiris-REx is like a robot explorer that flies in space and has special tools to grab a little piece of the asteroid so that NASA can study it and learn more about space. It's kind of like when you go to the beach and collect seashells, but instead of shells, they are rocks from space!
The asteroid that Osiris-REx is going to visit is called Bennu and it's very far away from Earth. Osiris-REx is going to fly to Bennu and take pictures and measurements to learn more about it.
Then, Osiris-REx will carefully grab a little piece of the asteroid using its special tools and put it in a special container. Then, Osiris-REx will fly back to Earth with the container full of asteroid pieces so that NASA can study them and learn even more about space!
So, in summary, Osiris-REx is a special machine that was built to explore a big rock called an asteroid and collect a little piece of it to bring back to Earth so that we can learn more about space. This will help NASA and other scientists understand more about our universe!