Understanding #statistics takes a thousand words while pictures paint a thousand words. The continuous flood of new MediaWiki messages at translatewiki.net is met by our localisers with varying levels of success. The reality of a localisation is experienced best by looking at the screens involved.
There are two ways to do this. You can change the language in your preferences, this may leave you a bit disoriented trying to find the preferences again to change them to something sensible or, you can add ?uselang=xx at the end of the URL.
When you do this for the main page of translatewiki, you will not only see the user interface change but also the main page itself localised. Both are localised by the Translate extension and benefit from all the specialised functionality that help localisers be efficient and provide the statistics that are a big help when decisions need to be made.