The global human settlement layer is like a big map that shows where people live all around the world. It is really important because it helps people understand how many people are living in each area and how those areas might be changing over time.
The map is made using lots of different pieces of information. People use satellite pictures and data from things like cell phone towers and electricity usage to figure out how many people are living in each spot. They can also see where buildings and roads are, which helps them understand how cities are growing and changing.
All of this information is put together in a big computer program which helps make the global human settlement layer. Then scientists and other people can use the map to learn more about how people are living all around the world. It can help people make better decisions about things like where to build new homes or how to make sure everyone has enough food and resources.
So, think of it like a big picture of the whole world that shows where people are living and how those places might be changing over time.