What do these PHP mbstring settings do?

I'm trying to figure out exactly what these php.ini settings do. What happens when they're set to different values? When are they necessary? When are they harmful?

• mbstring.language
• mbstring.http_input
• mbstring.http_output
• mbstring.encoding_translation

As usual, the PHP manual is less than helpful.

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You can change mbstring.language to whatever language you are using with. (Source)

language

; language for internal character representation.
mbstring.language = Neutral ; Set default language to neutral(UTF-8) (default)
mbstring.language = English
mbstring.language = Japanese
mbstring.language = Korean  ;For Korean market later

http_input

; http input encoding.
mbstring.http_input = pass
mbstring.http_input = auto
mbstring.http_input = UTF-8
mbstring.http_input = UTF-8, SJIS, EUC-JP

http_output

; http output encoding. mb_output_handler must be
; registered as output buffer to function
mbstring.http_output = pass
mbstring.http_output = UTF-8

encoding translation

; enable automatic encoding translation accoding to
; mbstring.internal_encoding setting. Input chars are
; converted to internal encoding by setting this to On.
; Note: Do _not_ use automatic encoding translation for
;       portable libs/applications.
mbstring.encoding_translation = On