When you look at the Earth, it's like seeing a big ball. And just like how a ball has two sides, the Earth has two big sides too. We can call these sides hemispheres.
One hemisphere is the land hemisphere, it's the half of the Earth that has the most land. It's like looking at a map and seeing all the countries, continents, mountains, and cities. You can see all the cool stuff people build and see on this side!
The other hemisphere is the water hemisphere, it's the half of the Earth that has the most water. It's like looking at a map and seeing all the oceans, rivers, lakes, and beaches. You can see all the cool stuff nature made on this side!
Now, the Earth spins around like a top, and when it does, sometimes the land hemisphere faces the sun, and sometimes the water hemisphere faces the sun. This affects the weather and seasons in different parts of the world, and it's pretty amazing how it all works together!