Done() function

Hello, guys.
Here i am, solving the MongoDB challenges that freeCodeCamp made avaible.
I quite understood the challenges (i’m in the last one), but i did not quite understand the done() function. I mean, i kinda know that it is a promise solving function. But can someone clearify it to me ? Like, write it to me?
function done() being called:

const createManyPeople = (arrayOfPeople, done) => {
  Person.create(arrayOfPeople, (err, data) => {
    if (err) {
      done(err);
    }
    done(null, data);
  });

};

Thanks!

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