Okay kiddo, have you ever heard of the game called "Jacks"? It's a fun game where you throw a small ball and pick up little metal pieces with different shapes called jacks.
Well, in the United States, there's something called the "Jack of the United States," but it's not a game. It's actually a sign that represents our country, just like a flag. The Jack is a special flag that is only flown on a special ship called the President's Flagship or the USS Constitution, which is like a really big ship that belongs to the President of the United States.
The Jack of the United States is made up of blue, white, and red stripes, just like the American flag, but it also has stars and an eagle on it. The eagle is a symbol of our country and represents freedom and strength.
So, when you see the Jack of the United States flying on the USS Constitution or any other ship in our Navy, it means that the ship is a part of our country's defense and represents the strength and freedom that we value so much.