The easiest way to create and work on an Ionic project is to use the Ionic CLI.
However Ionic 2 is based on Angular 2, so we could say that an Ionic project is basically an Angular project with the Ionic framework added to it. You don’t have to use the Ionic CLI.
Ionic “the framework” is one thing, and the Ionic CLI is another thing. This is an important distinction that people just starting with Ionic frequently seem to miss.