When setting up a legal entity in AX2012 you will need to consider the local functionality you will require for the entity. The local functionality in AX2012 is driven from a setting when you initially create the legal entity called the region code. This is associated with specific local functional and will turn on the features needed for that region. It’s important to understand language is a separate concept, changing the user language won’t change the functionality available to the user. This is a quick video to give you a quick walk through of the concept.
If you would like to understand more about this from a development perspective then here are some links that you might find interesting.
MSDN help Topic on the Country Context. On the left navigation in this topic you will see the link to the specific features associated with the different countries.
Whitepaper on applying country region as it applies to tables
MSDN help Topic on Applying Country context