Explanation

So, what I'm doing here is: I'm passing an arrow function to JavaScript's built-in filter() method on the Array.prototype object. This arrow function accepts a single argument that I can name anything I like (as long as I don't violate syntax rules of JavaScript). I named the argument person, since that's what each array item essentially is. Finally, I return the result of running a comparison between each person object's country property and the value of 'United States'.

The == operator checks for equality of type, and returns the boolean of true if the two values match, and the boolean of false if they do not match. Those person objects that passed the equality comparison - that is, those person objects that had the filter's callback function return the boolean of true after checking for equality between person.country and 'United States' - those person objects got pushed into a new array that gets returned from the filter() method call. Since these return array values do not change the source array in any way - that is, they are "non-destructive" - I had to save them as americans and brits - thus, essentially, splitting my source people array into two distinct subsets based on the country property of the people object.