Okay, so you know how America has 50 states? But did you know that there are also some places that belong to America but aren't actually states? One of those places is called American Samoa!
Now, because American Samoa isn't a state, it doesn't have its own member of Congress like the states do. So instead, American Samoa is treated as a very big "district" without any other states in it. This big district is called the "American Samoa at-large congressional district."
The "at-large" part means that there's just one person who represents American Samoa in Congress, rather than a bunch of people from different parts of the state like they do in the states. That person is called a "delegate," and they go to Washington, D.C. to speak for the people of American Samoa and try to pass laws that will help them.
So even though American Samoa isn't a state, they still get to have someone who speaks for them in Congress thanks to the at-large congressional district!