Okay, so you know how when you make a really important picture, you might use a fancy border around it? That's kind of like what the Preamble to the United States Constitution is - it's a sort of fancy border around the most important document in our country.
The Constitution is like a really big rule book for our country. It tells us how our government works, what rules we have to follow, and what rights we have as citizens. But before you get to all those rules and rights, there's this fancy border - the Preamble - that tells us why the Constitution was written and what it's supposed to do.
It starts with "We the People," which means that the Constitution was written by and for all the citizens of our country. It's sort of like a big team effort - everyone came together to write this rule book for our country.
Then it goes on to tell us what the Constitution is supposed to do. It says that it's supposed to establish justice (which means making things fair for everyone), promote the general welfare (which means making sure everyone is healthy, happy, and safe), and secure the blessings of liberty for ourselves and our posterity (which means making sure we're free and that our children and grandchildren will always be free).
So basically, the Preamble is like the fancy border around our Constitution. It tells us why the Constitution was written and what it's supposed to do. And just like how a fancy border makes a picture look important, the Preamble makes the Constitution look important too!