Heroku is a platform as a service that allows developers to deploy and scale applications. It focuses on being programmer-friendly by managing servers and allowing applications to be written in multiple languages like Ruby. Heroku supports over 4 million applications and the Ruby programming community. Customers like PicCollage and Voyagin have been able to easily scale their applications using Heroku's best practices. Developers can get started with Heroku for free and learn more through their documentation pages.