Baikonur Cosmodrome Site 31 is a special place where people shoot big rockets up into space. Imagine you are playing astronaut and you want to go to the moon. You need a special rocket to take you there because you can't just walk or drive there.
At Site 31, special people called rocket scientists and engineers make these big rockets. Then they load them up with things like satellites or people who want to go to space. Once everything is ready, they count down from 10 to 1 and then press a button that makes the rocket go blasting off into the sky!
Site 31 is really important because it's one of the few places in the world where they can launch these big rockets. It's located in a really big country called Kazakhstan and it's been around for a really long time - since 1955! A lot of big events in space exploration history have happened at Site 31, like when the first human went to space in 1961.
So, to sum it up, Baikonur Cosmodrome Site 31 is a special place where rockets are made and launched into space. It's a really important and cool place!