Oh hi there little buddy! So, have you ever heard of a place called Belarus? It's a country located in Europe. But before it was a country, it used to be a part of a bigger country called the Soviet Union.
Now the Soviet Union was made up of many smaller parts called republics, and one of those republics was called the Byelorussian Soviet Socialist Republic. It's a big name, I know, but it just means that the people who lived there believed in a type of government called socialism.
In this type of government, everyone works together to make sure everyone else has what they need, like food, healthcare, and education. It sounds nice, right?
Anyway, the Byelorussian SSR was a place where people from all different backgrounds and cultures lived together under one government. It was a pretty important part of the Soviet Union and had a lot of different industries, like farming, manufacturing, and mining.
But eventually, the Soviet Union broke apart, and all the different republics became their own countries. So, the Byelorussian SSR became the independent country of Belarus that we know today.
That's the ELI5 explanation of the Byelorussian Soviet Socialist Republic!