Gettext is the localization(L10N) library and tools which is modeled after GNU gettext package.
This library was called as "Ruby-GetText-Package". Since 2.3.0, this library is called just "gettext". You can call this library as "gettext gem" or "Ruby gettext" to distinguish from GNU gettext.
The library converts the messages to localized messages properly using client-side locale information such as environment variable and CGI variable.
And the tools for developers support to create, use, and modify localized message files (message catalogs) easily.
Locale is the pure Ruby library which provides basic and general purpose APIs for localization.
This library was called as "Ruby-Locale". Since 2.0.6, this library is called just "locale". You can call this library as "locale gem" or "Ruby Locale" to distinguish from other "locale"s.
This library aims to support all environments which Ruby works and all kind of programs (GUI, WWW, library, etc), and becomes the hub of other i18n/l10n libs/apps to handle major locale ID standards.