This is language of the messages the system displays to the user.

To control the available languages you edit /etc/locale.gen and remove the comment for locale(s) to be generated (UTF-8 is the recommend choice).

TIP: To save and exit press F2 y Enter.

# nano /etc/locale.gen

Select locale
Example for a system in Denmark using english messages

#en_CA ISO-8859-1
en_DK.UTF-8 UTF-8
#en_DK ISO-8869-1

TIP: uncomment the locale en_US.UTF-8 UTF-8 as a fallback locale.

Generate the messages

# locale-gen

Edit your locale configuration in /etc/locale.conf to match above choice - example for Denmark

# nano /etc/locale.conf