Okay kiddo, imagine you're breathing out hot air when you speak. That air is made up of tiny particles called "vapor." "Vapor" is just a fancy word that means tiny little droplets of liquid that are floating in the air.
Now, let's talk about how water turns into vapor. When water gets really hot, like when you boil it on the stove or when the sun shines on a puddle, some of that water starts to turn into vapor. The water molecules start to jump around really fast and they break free from each other to become part of the air. This is called "evaporation."
You can see this happening when you breathe on a mirror or a window. The warm air from your breath hits the colder surface of the glass and turns into tiny droplets of water, or "vapor."
Vapor is all around us, but we can't always see it. When you take a hot shower, the steam you see rising up is actually water vapor. And when you blow on your soup to cool it down, the steam that comes off is also vapor.
So, in short, "vapor" is just a fancy word for tiny droplets of liquid that are floating in the air. It happens when water gets really hot and turns into a gas.