Microsoft has long suffered from a lack of a configurable portal layer for Dynamics CRM. While the core product allowed you to design forms and custom entities for use by employees, developing self-service portals that were customer facing was not easily done without custom .NET code.
ADX Studio has been filling the gap by providing a third party solution that extends Dynamics CRM into self-service portals. The solution is a .NET based solution that allows developers to build robust portals with authentication, data entry forms, surfacing of CRM data, etc. without the need for extensive development. The solution reads the CRM schema dynamically so that if you change the underlying CRM model it is reflected automatically in the portal.
Microsoft has just acquired ADX Studio and will be integrating it into the core Dynamics product. Along with the recent acquisition of FieldOne, this means that gaps in the product that were previously being filled by third party applications will now be integrated as in house solutions.