Classical elements are basically different types of things that ancient people believed everything in the world was made up of. There were four classical elements: earth, water, air, and fire.
The element of earth represented anything solid, like rocks or dirt. The element of water represented anything liquid, like rivers or oceans. The element of air represented anything gas, like the wind or your breath. The element of fire represented anything that gave off heat and light, like a candle or the sun.
These elements were believed to be the building blocks of everything in the universe, even people and animals. Different combinations of these elements would create different things. For example, a tree could be made up of earth, water, and air, while a flame could be made up of fire and air.
Although many people today don't believe in the classical elements anymore, they were very important to understanding the world a long time ago. Nowadays, we use different types of science to explain how things are made up, but the concept of the classical elements is still interesting to learn about!