.env.example file is a template of the
.env file that you can use to define environment variables for your project. It is ignored by Git because each developer / server using your project can have its own configuration.
This file can be renamed to
.env.local and used to load environment variables. The environment variables defined in this file are the ones that will be loaded in your project if you don't set them up in your server.
Read more about environment variables in the Next.js documentation.
In the future, this file will be used to show more examples on how to configure Shipixen for a newsletter, etc.