Hey buddy, have you ever been outside in the winter and it's really, really cold? Like, so cold that everything is frozen and covered with snow? Well, a really long time ago, a lot of places in the world were like that all the time, even when it was supposed to be warm.
This happened a long time ago, when some people called the Romans were in charge of a big part of the world. They had something called the "Roman Empire" and a lot of people lived there. But around the year 536, everything started to get really cold. The sun wasn't as bright as usual, and it was harder for people to grow crops and get food.
This cold time lasted for a few hundred years, and it was called the "late antique little ice age." It was really hard for people to live during this time, because they didn't have things like central heating or warm clothes like we do today. They had to figure out ways to stay warm, like building fires and wearing lots of layers of clothes.
Even though it was a really tough time, some good things came out of it, too. People had to learn how to be more self-sufficient and figure out new ways to get food and take care of themselves. And eventually, the world got warmer again and things went back to normal.