fastboot usage example explained?

Can some one please explain in more detail how the example posted in the "Fastboot" readme file would work, as to where in an existing Ember application this would be integrated? Thanks.

This is a copy of the code I don't understand:

// Usage
const FastBoot = require('fastboot');
 
let app = new FastBoot({
  distPath: 'path/to/dist'
});
 
app.visit('/photos')
  .then(result => result.html())
  .then(html => res.send(html));