The 35 languages are included on the "Windows Server <version> Language Pack (x64)" DVD that can be installed on top of an existing version to provide a localized experience and language switching. The DVD is available through Volume Licensing or MSDN downloads. Language Packs provide a localized experience for "Remote Desktop/Terminal Services" scenarios only. Most administrative features are not available nor supported in a language other than the base language of the server. The extent of localization in any given language will match the above list. This means that installing the French Language Pack will provide a similar level of localization as installing the French Server product, while installing the Croatian language pack will only provide localization for "Desktop" features.
Most System Center 2012 and System Center 2016 products are available in the same 18 languages as Windows Server (marked "Full" or "Full except PowerShell" in the above table)