Stand-your-ground law says that if you feel like someone might hurt you, you don't have to run away. You can stay where you are and try to protect yourself.
So let's say you're at the park with your mom and you see a big, scary dog coming towards you. You feel like the dog might hurt you, so you yell for your mom and stand your ground instead of running away. If the dog does attack you, you can try to defend yourself without getting in trouble.
But the important thing to remember is that this law only works if you are acting in self-defense. You can't just go up to someone and start a fight and then say you were protecting yourself. That's not how it works. You have to be in danger and have no other choice but to defend yourself.
If you're ever in a situation where you feel like you might need to defend yourself, it's always best to talk to an adult and get help. They can help you figure out what to do next.