Nature includes everything in the world that is not human or man-made. Things like mountains, rivers, trees, and rain are all part of nature. Scientists study the way the parts of nature work.
Many people enjoy looking at natural things or walking in natural places, but people also have to think about how they want to use nature. Or, how they can be useful to it. Some people see reforesting and wild gardening as ways to be useful to nature.
This means they must know how it works, and how it affects the air, soil, water, plants, animals and their own body. The science of ecology is about their connection, while biology studies the parts. These are two of the Natural Sciences. They create models of nature. The science is covered in that article.
In many ways humans and nature can be said to be in conflict. Nature is often seen by humans as natural resources:
People cut down trees to get wood to burn or to build houses, or to make a place to grow food. Fires, cars, and factories make a lot of smoke, especially in cities. When people catch a lot of fish, sometimes they kill all the fish or harm the spawning grounds and there are none left. For instance the trawling method of catching fish very often damages coral that the small fish need to hide from big ones.
People who like to leave nature unharmed and those who feel they need to use more of nature often fight about what they should do. In the modern world, with many people and many big cities, these problems are becoming more serious. It takes politics to sort them out fully.