Depopulation is a scary word that some grown-ups use when they talk about having fewer people in a certain place. Let's imagine we have a big bowl of candy with lots and lots of candies in it, and we want to have fewer candies in the bowl. That's kind of like what depopulation means, but instead of candies, it's talking about people.
Sometimes people talk about depopulation when they are worried about a place having too many people and not enough resources, like food or water, for everyone to live comfortably. Other times, people might talk about depopulation when they're worried about diseases spreading really easily in a crowded place and making lots of people sick.
In some cases, depopulation can happen naturally when people decide to move away from a certain place in search of better living conditions or job opportunities. But unfortunately, sometimes depopulation can be caused by really bad things like wars, natural disasters, or diseases.
Overall, depopulation means having fewer people in a certain place, and it can happen for different reasons - sometimes it's good, sometimes it's bad, but it's always something grown-ups are worried about.