Creating an emberjs project in Heroku

I followed these steps to create an ember project on Heroku: http://ift.tt/1SyI5bJ

$ git clone git@github.com:heroku/ember-js-getting-started.git
$ cd ember-js-getting-started
$ heroku create --buildpack http://ift.tt/2oiBVbe
$ git push heroku master
$ heroku open

My question is, after I clone the repository, what exactly does the line: heroku create --buildpack http://ift.tt/2oiBVbe