The user's LANG environment variable is important for two reasons:
The value of LANG is used to locate the correct help volume.
When a help topic is displayed, the correct fonts and formatting rules are chosen based on the user's LANG variable. This is especially important for Asian languages that have word-wrap rules that are more sophisticated than European and American languages.
CDE Internationalization Programmer's Guide
NLS documentation for your computer's operating system or programmer's kit