Is not clear to CMS on yii
specifically You do not understand?
Information on CMS in the network
of course not, yii is a framework, and often it write a cms for a specific project. And not something like wp on than you can stir up anything. In this sense, there is nothing extra and it works fast.
where yii are the files responsible for the layout of the site, the view, the view, the HTML is shorter...
depends on the version and the developer's imagination. Usually there is a folder view, if the layout is advanced and version 2, then /frontend/views
there is documentation www.yiiframework.com
But it will be easier if you show your structure, then give a precise answer.
Why not refer the matter to the developer or to entrust him with this?