A 99-year lease is like borrowing a toy for a really, really long time. It's like when your friend lets you play with their toy for a whole day, but instead of one day, it's for 99 years!
So, let's say you want to play with your friend's toy house. Your friend says you can have it for 99 years, but after that, they want it back. That means for 99 years, you get to play with the toy house, and after that, you have to give it back to your friend.
But while you have the toy house, you can do whatever you want with it, just like if you were borrowing your friend's toy. You can decorate it, make it your own, and even rent it out to other people.
People use 99-year leases for things like land, homes, or buildings. It's like renting or borrowing something for a really long time, but eventually, you have to give it back to the original owner.