Device manufacturers can find details about deployment options for language packs at Add Language Packs to Windows.
To reduce disk space requirements in Windows 10 and improve installation time, language packs have been split into language components and Features on Demand v2 (Capabilities). Language components include the user interface text for that language and basic Cortana capabilities. Other language features, including spell checking, text prediction, word breaking, hyphenation, fonts, optical character recognition, handwriting recognition, text-to-speech, and speech recognition are installed as needed using Features on Demand v2 (Capabilities). See KB 3109599 for Features on Demand v2 (Capabilities) available for Windows 10 Version 1511. Device manufacturers can find details for deployment options at Features On Demand V2 (Capabilities).
Language interface packs include Windows user interface text for a region, and can provide a better experience in countries or regions where two languages are commonly used. LIPs require at least one language pack (or parent language) to install. For example, the Catalan (ca-ES) language interface pack can be installed only if one of the following languages is already installed: English US (en-US), Great Britain (en-GB), Spanish (es-ES), or French (fr-FR).
For a list of the LIPs and their parent languages, see Available Language Packs for Windows.