Freedom of speech in the United States means that people have the right to say whatever they want without getting in trouble with the government. This is written in the Constitution, which is like the boss of the country's laws.
So, let's imagine you're playing in a park with your buddies and you want to say, "I love playing with my friends!" That's freedom of speech! As long as you're not hurting anyone and not breaking any laws, you can say whatever you want!
Now, if you say something mean to someone or something that could hurt them, that's not okay. Just because you have freedom of speech doesn't mean you should use it to be mean or hurt people's feelings.
Also, freedom of speech doesn't mean you can say whatever you want everywhere you go. For example, if you go to your school and start shouting things that could be dangerous or disruptive, you could get in trouble. Schools and other places can have rules about how you talk and what you can say.
Overall, freedom of speech means you have the right to speak your mind, but you should use it in a responsible way that doesn't hurt others.