Copyright law is like sharing your toys with others. Just like how you don't want others to take your toys and play with them without your permission, artists and writers don't want others to use their creative works without permission.
So, the law in the United States says that authors and creators have the exclusive right to use their work and decide who else can use it. This means that nobody can copy or share their work without their permission. If someone does, that's called copyright infringement, which is breaking the law.
Copyright law also gives creators the right to make money from their work. For example, if I wrote a book and someone wants to sell copies of it, they have to pay me a fee or a royalty.
But, there are some exceptions to copyright law. For example, it's okay to use someone's work for educational purposes or create something new from someone else's work. This is called "fair use."
So, just like you want others to ask before playing with your toys, it's important to ask for permission before using someone else's creative work. If you don't, you could get in trouble with the law.