Following are the links that explains Procfile and Foreman.

[Foreman Manual][1]

[Introducing Foreman][2]

[Declaring and Scaling Process Types with Procfile][3]
[1]: https://devcenter.heroku.com/articles/procfile#developing_locally_with_foreman
[2]: http://blog.daviddollar.org/2011/05/06/introducing-foreman.html
[3]: https://devcenter.heroku.com/articles/procfile#scaling_a_process_type