CLI's gain an extra level of power when you realize they can start and manage other CLI's and run multiple concurrent child processes (great for farming out work on multi-core machines!). You can even use it to improve developer experience in really small ways. For example, create-react-app famously scaffolds out a React app for you, and also installs the relevant node_modules. We'll learn how to do this two ways: with execa and with a dedicated yarn-or-npm utility, because this is such a common usecase.
But before all that - we must learn and be comfortable with the raw Node.js child_process and I/O Stream API's. So that's where we begin.