Labour supply is like your toy box. You have lots of toys in your toy box, but which ones you choose to play with depends on a few things. If you feel tired or sick, you might not want to play with any toys. But if you have lots of energy and feel good, you might choose to play with your favourite toys.
Grown-ups have something called a "labour supply" which is like their toy box. Instead of toys, they have skills and abilities that they can use to work and earn money. Just like you choose which toys to play with based on how you feel, grown-ups choose how much they want to work based on a few things too.
For example, if grown-ups are tired or sick, they might not want to work at all. But if they feel good and have lots of energy, they might choose to work more. And just like how you might really want to play with a certain toy in your toybox, grown-ups might really want to work at a certain job because it pays well or because they enjoy doing it.
So, labour supply is all about how much work grown-ups choose to do based on how they feel and what opportunities are available to them. It's like they get to choose which toys to play with, but instead of toys it's their job and how much they want to work.