Architecture is nothing but the flow of data from one part of the application to another part or one application to another application to complete the operation and get expected result. Any application/program has its own way of working and its own architecture. AX architecture is defined for extracting the best performance out of the application and makes the user get best experience working with AX.
In Microsoft Dynamics AX, there is a 3-tier infrastructure with a database server, an application object server (AOS), and a client.
As from the above figure, Tier One is the client where users work. This holds the UI.
In the above figure, UI or client is called as MorphX. This is IDE which is used to communicate with AX server. Custom AX development and modification is done with its own IDE, MorphX, which resides in the same client application that a normal day-to-day user would access, thus allowing development to take place on any instance of the client. Since the Dynamics AX 2012 version, development can also be performed in Microsoft Visual Studio 2010 through a Visual Studio plug-in.
MorphX is an integrated development environment in Microsoft Dynamics AX that allows developers to graphically design data types, base enumerations, tables, queries, forms, menus and reports. In addition to design of application objects, it also allows access to any application code by launching the X++ code editor.
An Application Object Server (AOS) is a core component of the Microsoft Dynamics AX 2012 installation and is installed by using Setup. An AOS enforces security, manages connections between clients and the database, and provides the foundation where Microsoft Dynamics AX business logic is executed. An AOS is implemented as a Microsoft Windows Service and is listed in the services as
Finally, backend tier is used to store the data. AOS will not store any data except executing business logic and communicate with backend to get and store data. Usually, Microsoft SQL Server 2005 is used for AX 2009 and Microsoft SQL Server 2008 is used for AX 2012 for storing data.