Okay kiddo, so you know that the Earth's climate can change over time, right? Well, a really long time ago, about 20,000 years ago, there was a time when it was really cold all around the world, especially in the northern parts. This was called the "late glacial maximum."
During this time, a lot of the Earth's water was frozen in big glaciers or ice sheets, like giant blankets of ice covering huge areas of land. Because of this, the sea level was lower, and some places that are now underwater were actually dry land!
A lot of different animals and plants had to adapt to this cold climate or they died out, and some of them became extinct. People who lived during this time had to find ways to survive in the freezing conditions, and they had to move around a lot to find food and shelter.
But eventually, over thousands of years, the climate started to warm up again and the ice started to melt. This led to big changes in the environment and in the animals and plants that lived there. And that's a summary of the late glacial maximum, my little friend!