JS return structure

What is the difference between {} and ( ) in JavaScript's return statement?

const fruits = [
  {
    name: "FaceBook",
    nickname: "FB",
  },
  {
    name: "Youtube",
    nickname: "YT",
  },
  {
    name: "AmazonWebService",
    nickname: "AWS",
  },
];
const count = fruits.reduce((acc, cur) => {
  return { ...acc, [cur.nickname]: cur.name };  // What does {} of return mean here?
}, {});