What JS Syntax is this and what does it mean?

Question

First of all, sorry for the redundant question, just haven't found a proper way to ask this. I was checking out a video for protecting routes using React-router when the dude in the video wrote something like this:

class Auth {
  constructor() {
    this.authenticated = false;
  }

  login(cb) {
    this.authenticated = true;
    cb();
  }

  logout(cb) {
    this.authenticated = false;
    cb();
  }

  isAuthenticated() {
    return this.authenticated;
  }
}

Here's the bit that's confusing me:

login(cb) {
  this.authenticated = true;
  cb(); // What syntax is this???
}

What does this do exactly do? Is it supossed to take a function as an argument call her? Thanks for your help in advance!