Heroku is a Platform-as-a-Service (PaaS) that exists on the cloud, allowing software developers to build and run complex web applications without having to worry about the underlying hardware or the networking aspects of it.
I've been using Heroku for more than three years for some personal projects (small and big ones) and I truly recommend it for several reasons that I will explain below. Of course, this tool isn’t a silver bullet for cloud deployment; you will always need to know your needs in a project before choosing a tool to achieve it. Also, this is not any promoted article by SalesForce, I’m doing it for free because this tool really helps me almost every day to get things done in an easy way.