A mole is a counting unit, kind of like how you count toys or candies. But instead of counting toys or candies, we use moles to count teeny-tiny particles called atoms or molecules.
Atoms and molecules are like little building blocks that everything in the world is made out of. There are lots and lots of different types of atoms and molecules.
The number of atoms or molecules in one mole is a really big number called Avogadro's number (6.02 x 10^23). That's like trying to count how many stars there are in the sky, but there are so many you can't even imagine!
By using moles, scientists and chemists can talk about how much of a substance they have in an easier way. For example, instead of saying "I have 602,000,000,000,000,000,000,000 water molecules", they can just say "I have one mole of water".
So, a mole unit is just a fancy way to count tiny building blocks, making it easier for scientists to communicate about them in experiments and studies.