Hi Vienna! That's a great question! Let's break it down step by step.
First, when we say the Earth is round, we actually mean it’s shaped like a ball or a big sphere. Imagine a basketball. Even though it looks round, at the same time, there are parts of that basketball that are 'on the bottom' when you're standing on a flat surface. So, when you think about parts of Earth being 'upside down,' it’s because you might think of them based on where you are standing!
But the fun part is that there is no 'up' or 'down' in space like we usually think of it. For example, someone standing in Australia is 'upside down' if you’re thinking from your perspective in America, but to them, everything is right side up!
Now, about the water staying on Earth: that’s all because of something called gravity. Imagine that the Earth is like a giant magnet; this magnet pulls everything towards its center. This means anything that’s on the surface, including you, me, and water, gets pulled in and held tight to the ground. That’s why when you jump, you always come back down instead of floating away!
So, to sum it up: the Earth is round, and it looks different depending on where you are. Gravity is the force that keeps everything, including water, from floating away. Isn’t that cool?