Hund's rules tell us how electrons behave in atoms. Just like how you have your own toys and like to keep them in a certain order, electrons also have some rules they like to follow.
First, electrons don't like to share their toys - this means that if there is an empty box for an electron to fill up, the first electron will go in all by itself before another one joins.
Second, electrons want to be as happy as possible, just like how you like to be happy when playing with your favorite toys. So, when there are different boxes for them to go into, electrons will fill up the boxes one by one with their own kind before having to share a box with another electron. This means that, if there are three boxes and three different types of electrons (let’s call them A, B, and C), the first electron will go into the first box (let’s call it box 1) and be all by itself. The second electron will go into the second box (let’s call it box 2), because it's the same type as the first electron. The third electron has to go into the third box (let’s call it box 3) and share it with the first electron, making both electrons happy.
Finally, when there are empty boxes, electrons don't like to jump around - this means that when there is a box that needs an electron, the electron will try to stick to the box that's already got other happy electrons before moving to a new box.
Overall, these rules help explain how electrons behave in atoms, and why they can form chemical bonds and make our world interesting!