At this stage, our app is ready, we are using it happily (doing all the stuff we want), and everything is on my machine. Life is easy, but what happens when a friend or cousin, after watching this, wants to use it on their machine? In other words, your app is ready and you want it to be used by anyone in the world. So to achieve this, you have to place it somewhere so that anyone can use it; this somewhere could be a public server. You have to set up your app there so that it can run and anyone can use it; this setting up process is called deployment.

Deployment includes all the operations and necessary changes required to prepare the app for a running environment and ready to be used by end customers.

To ensure that our app will deploy and run successfully, we must first ensure that all the components on which our app is dependent (such as configuration variables) are already installed on the remote server.

Thanks to Heroku, all the basic necessary setup is already done for us;...