So, RSM-56 Bulava is a fancy name for a really big and powerful missile that Russia uses to protect itself.
The Bulava missile is like a really long tube filled with explosives, kind of like a big firework, but way more powerful. It can go really high up in the sky and then come down really fast to hit its target with a big BOOM!
The reason Russia has the Bulava missile is to make sure nobody tries to attack them. It's like a big flashlight that they can shine in the eyes of anyone who wants to do them harm, because nobody wants to mess with a country that has such a powerful weapon.
Overall, the Bulava missile is a very important tool for Russia to keep itself safe and protected from any threats that might come its way.