The classical elements are like flavors that make up everything in the world. Just like how we know about sweet, sour, salty, and bitter flavors, ancient people believed that there were four basic flavors that made up everything in the world. These four flavors were fire, water, earth, and air.
Fire is what makes things hot and gives us light. It's like the spicy flavor in our food. Water is wet and flows, like the flavor of something juicy. Earth is solid and doesn't move easily, like a flavor that's crunchy or hard to bite into. Air is what we breathe and moves around easily, like a flavor that feels light and airy.
Ancient people believed that everything in the world was made up of different combinations of these four flavors. They used this idea to explain things like why some things were hot or why some things were solid. Even though we know more about science now, some people still use the idea of classical elements as a way to understand the world around us.