Buy Nothing Day is when we make a promise to not buy anything on a particular day. It's like taking a day off from spending money to help us think about how much we spend and maybe save some money. When we buy things, we use up resources like electricity, water, gasoline, and other items that have to be made, shipped, and sold. Buying things can also create waste, which harms our planet. So, by not buying anything on Buy Nothing Day, we can help protect the environment and become more aware of our shopping habits.