Think of your favorite pair of jeans. They're tough, they're reliable, and they hold everything together. That's basically what the blue on the flag is doing. It's the union—the place where all the stars come together to hang out.
In flag terms, they call it the "union" or the "canton." But to me, it’s like the group chat where all fifty states are having a conversation. It's the glue that keeps the red and white stripes from just flying away in chaos.
