Following is architecture diagram I took from white paper.
You can download white paper from following link.
Enterprise portal is based on Standard flexible ASP.net controls used in web parts and Share point portal. Dynamics Ax 2012 serve as data source. These data sources are written in X++ exposed to web controls through proxy classes or meta data API.
Enterprise portal is based on Web part framework of SharePoint. These web parts are easily customizable and personalized. Microsoft AX web part are used to expose the Dynamic Ax functionality.
These web parts can contains both Dynamics ax web controls like AXGridView and standard asp.net web controls like textbox.