There are several layers in AX and the customization’s that you develop according to your industry requirement on top of the default out of the box (AX) product must be developed and delivered in ISV layer. There are certain qualifications to become ISV partner.
First to get an understanding about what’s Retail functionality that AX is offering. You can begin downloading the brochures, case studies, feedback available online and to get some idea just walk through videos on AX retail. Probably that should help you to begin exploration.
organicax.com/…/
www.youtube.com/results
BTW -Welcome to Dynamics AX-ERP world.