Okay, imagine you and your friends are playing music together. Normally, you might have someone, called a conductor, who waves their hands to show everyone when to start and stop playing. But sometimes, there is no conductor, and that's okay!
In this case, one of your friends becomes the leader, like a big brother or sister, and they help everyone else know when to play and when to pause. They might nod their head or tap their foot to make sure everyone is playing together nicely. This way, even without a conductor, everyone still has fun making music together with a nice beat!