This package manages culturally-determined typographical (and
other) rules for a wide range of languages. A document may
select a single language to be supported, or it may select
several, in which case the document may switch from one
language to another in a variety of ways. Babel uses
contributed configuration files that provide the detail of what
has to be done for each language, as well as .ini files for
about 300 languages from around the World, including many
written in non-Latin and RTL scripts. Many of them work with
pdfLaTeX, as well as with XeLaTeX and LuaLaTeX, out of the box.
A few even work with plain formats.