The basics of localization and internationalization are explained in The FreeBSD Handbook, more specifically Chapter 13, Localization - I18N/L10N Usage and Setup and 13.3 - Using Localization.
In short, a locale is a set of files that lets the OS use the appropriate format for date, time, numbers, character classes (letters, numbers, whitespace, uppercase and lowercase characters) and other information that is different for different countries or languages.
The bg_BG.CP1251 locale, as suggested by its name, determines the locale settings for Bulgaria (BG), using the Bulgarian language (bg) and the CP1251 codepage, also known as windows-1251. If you configure your system to use it, the OS will recognize correctly Cyrillic characters as letters, display day and month names in Bulgarian, use the Bulgarian currency unit - 'lev' - where appropriate, and more.
Note: To use the bg_BG.CP1251 locale, you might need a Cyrillic screen font and a keyboard map that will allow you to enter Cyrillic (CP1251) characters. See the Bulgarian fonts and keymaps section for more information how to do this with FreeBSD.
Patches for bringing the bg_BG.CP1251 locale into FreeBSD are available for the 4.x branch up to 4.4-STABLE-20011210 and for the 5.x branch up to 5.0-CURRENT-20011105. These patches were integrated into FreeBSD on 2001/11/05 for 5.0-CURRENT and on 2001/12/10 for 4.4-STABLE. Thus, the good news is that the bg_BG.CP1251 locale will be natively supported in both both 4.5-RELEASE and 5.0-RELEASE.
FreeBSD 4.x before 2001/12/10, including the 4.1, 4.2, 4.3 and 4.4 releases
FreeBSD 5.0-CURRENT before 2001/11/05
This, and other documents, can be downloaded from ftp://ftp.FreeBSD-bg.ringlet.net/pub/FreeBSD-bg/doc/.
For questions about FreeBSD, read the
documentation
before contacting <questions@FreeBSD.org>.
For questions about this documentation, e-mail <doc@FreeBSD-bg.ringlet.net>.