Mobile layouts in the CMS/LMS are essentially done with responsive design meaning that we use media queries and CSS to automatically detect and style the layout for mobile.
Beyond that we support exception styling where you can have various screen sizes have special CSS.
To even begin to understand this you first must have a good understanding of CSS in general.
For now, just understand that the mobile layout is not a separately coded layout but derived from rules applied to the normal desktop layout. We can override some of this to tweak oddities that occur on the mobile device but only to a point.