Okay kiddo, so let's talk about Varangians! The Varangians were a group of people from northern Europe (places like Sweden, Norway, and Denmark) who were really good at fighting and sailing. They didn't always have a lot of money or land, so sometimes they traveled to other places to find work and adventure.
One place where Varangians were especially popular was in the Byzantine Empire. This was a big, powerful civilization that ruled a lot of the land around the Mediterranean Sea in the olden days. The Byzantines thought the Varangians were really tough and brave, so they hired them to be soldiers and guards.
The Varangians who went to work for the Byzantines were called the "Varangian Guard." They were supposed to protect the emperor and the palace and make sure nobody bad could get in. The Varangian Guard were really famous for their fighting skills and cool weapons, like big axes and long swords.
Being in the Varangian Guard was a pretty big deal for a Varangian, because it meant you got to live in the coolest place in Constantinople (which was the capital city of the Byzantine Empire) and have lots of nice things. But it was also dangerous, because sometimes the Varangians had to fight in big battles, and sometimes other people didn't like them very much.
So that's what Varangians are, kiddo. They were a group of tough warriors from northern Europe who went to work as soldiers and guards for the Byzantine Empire.