There are three applications in advanced template: frontend, backend and console. Frontend is typically what is presented to end user, the project itself. Backend is admin panel, analytics and such functionality. Console is typically used for cron jobs and low-level server management. Also it's used during application deployment and handles migrations and assets.
There's also a
common directory that contains files used by more than one application. For example,
Frontend and backend are both web applications and both contain the
web directory. That's the webroot you should point your
web server to.
Each application has its own namespace and alias corresponding to its name. Same applies to the common directory.