As you may already know the e2e stands for the end-to-end tests. And the ng e2e is building a serving a project and then it triggers Protractor to run e2e tests.
To use it you need to specify the project, like this
ng e2e my-project
Then you will be given with the following CLI log
As you can see after calling the selenium the server opens on the http://localhost:4200
At the same time, the test responds with SUCCESS.