AX uses the registry on the local computer of the client when it needs to know information about how the client is configured.
To set this up for each user has been quite tedious and often we have just created axc files with the configuration and put it on a file share. The problem with that approach is that neither AX itself or other applications have any means to figure out details of the client configuration. Two examples of applications that would benefit of knowing this is Visual Studio and MS Project.
In AX 2012 the configuration tool is extended with a bridge between the two methods of pointing to the configuration. This is called Configuration Store and with this you point out the axc file on the share, in the client configuration utility. So AX and other applications still knows about the active configuration through the registry, but you only need to apply configuration changes to the axc file on the file share.
Read more about the possibilities for shared client configurations here on TechNet: http://technet.microsoft.com/en-us/library/hh378075.aspx
This may be old news if you work a lot with AX installations, but it was new to me and I hope I wasn't the last to know.