Indexing language and installed languages

unknown

My trial JIRA showing English- Moderate Stemming as Indexing language, so wonder what this for ?

any requirement from database to match this ?

Secondly,  how can remove installed languages as we only deal with English; while I don't even know how to enable other languages and what can be seen , just the display change ? 

a bit confused about Internationalization section in system setting , perhaps I only understand Default language and Default user time zone. Please advise my initial installation, must be something I can adjust ?  

Ignacio Pulgar

The indexing language is relevant for how Lucene stores words and special characters, which is the technology that powers text searches in JIRA.

Why would you need to prevent users from displaying the User Interface in the language they want? I don't think it would save a significant amount of resources, and it's a nice feature to have in place just in case you were visited by a foreigner guest.