Run is a command that triggers what is possible in the project via the architects’ key specification. You need to pass the project name and one of the possible architect keys to use it.
Showing this on an example if you are inside the project category my-project you can run
ng run my-project:build
Why? Let’s check the angular.json file for hints.
As you can see in the 12th line there’s a specification for the architects key. It has 6 children objects
It means that I can pick and of those commands from the run architect target.