Zend Expressive is the latest iteration of Zend Framework. Like a lot of modern frameworks, it supports a lot of command line tooling to make life easier when bootstrapping applications with it. In Zend Expressive’s case, when creating new applications, you can use the Zend Expressive Skeleton Installer to rapidly create a new application that is ready-to-go with basic routing, dependency injection, templating, and error handling. While that can be a logical way to go, it’s not the only way. You don’t need to use the Skeleton Installer. You can create applications by hand.