From Joomla! Documentation
Pages marked for translation are called message groups. They are broken down into smaller 'messages' to make translating a page easier. Click on your language statistic link below to see the message groups (pages) statistics (untranslated message groups vs. translated message groups) for your language. You can then click on a message group (page) and start translating the individual messages.
Make sure your language is localised to you or when translating, set the translation to language in the top right.
- Currently, translators are working on the Joomla! Glossary Terms. Please translate the Chunk:<term> first, then the terms without the Chunk: prefix.