Confusion on directory structure

I am creating my first of many Yii apps.

I am planning to use this project structure - http://www.yiiframework.com/wiki/155/the-directory-structure-of-the-yii-project-site/ in my app.

Is it only the folders components, models, lib I can keep in the common directory and be able to use in both frontends and backends? Or can I do the same for other folders like modules too?

I’d highly appreciate if anyone provides a sandbox for this structure.

Regards!