Fee simple is like being the king or queen of a piece of land. You can use it however you want, and nobody can take it away from you.
Say you have a very special toy that is all yours. Nobody can take it away from you, and you can play with it whenever you want. That's like a fee simple ownership of land.
When you own land in fee simple, you can build houses, plant gardens, and even sell it to someone else. You have complete power over it because it's all yours.
However, just like with your toy, it's important to follow rules and be responsible for your actions. If you don't take care of your toy, it might break. If you don't take care of your land, it might lose value or get taken away through a legal process.