The Interface Customizations section not only allows you to specify languages but gives you the power to change the terms you would like to use.
For example, rather than calling a lead “New Lead Opportunity” you can change it to “New Potential Client” etc. This would be accomplished by adding the rule; Group “lead-new” Key “email.title” Translation “New Potential Client” Locale “English”.
The Translation field is where you populate the information you want to be displayed and the Locale field is used to define what language an agent’s profile must be set to in order to see your translations.
While this functionality is powerful and allows for more than just agent facing screens to be changed, it is also best to contact Support for the list of groups and keys required to make the changes you want.