When you install the Dart SDK, one of the tools that you get is pub. The pub tool provides commands for a variety of purposes. One command installs packages, another starts up an HTTP server for testing, another prepares your app for deployment, and another publishes your package to pub.dartlang.org. You can access the pub commands either through an IDE, such as WebStorm, or at the command line.
For an overview of these commands, see Pub Commands.