A family of Microsoft word processing software products for creating web, email, and print documents.
There has been a progression from one version to the next in this regard. In earlier versions, the Proofing Tools were a single huge package (rather expensive) that included proofing tools for every available language. It was not possible to buy Proofing Tools for a single language at a lower cost. Users complained about this. The Proofing Tools package offered only proofing tools; it did not provide for changing the language interface, which required a different package.
So Microsoft tried a new tack, offering Language Packs (which include the language interface, if desired, along with the proofing tools) for specific languages à la carte. Then users complained about having to pay for each language separately.
Office 2013 finally gets it mostly right, offering Language Packs à la carte for any language at no charge.
Meanwhile, Microsoft has been expanding the number of languages served. There is not a Language Pack for every language, but there are Language Interface Packs (just the UI, no proofing tools) for a lot of less-used languages, and languages are constantly being added. It is no small trick to translate the UI of every Office program into another language, and MS doesn't always get it right. For example, there's currently a complaint on file because the Danish-language version uses the wrong word for "website" in citations ("Hentede" instead of "Hentet").