Heroku is a platform-as-a-service that runs applications on AWS instances located in the US-East and EU-West regions. To deploy an app on Heroku, developers first create an Heroku account, install the Heroku Toolbelt CLI, and clone a sample project. They then create a Heroku remote, push their code to both GitHub and Heroku using git, and open the deployed app in a browser via its Heroku URL.