Language template variables are placeholders for text to be filled in by the appropriate language pack. If you selected at least one non-English language during installation, your templates have language variables to separate language from templates so that you can use multiple languages with the same templates, and to make it easier to translate. If you only selected English during installation, you do not have language template variables used in your templates but instead your templates are filled with English text to be easier to read.

Language template variables can be customized in the Admin -> Customizations -> Language area of your admin panel. You can add new ones there or change the content of existing ones.

Displaying a languge item is simple. In any template, type {LANG_ followed by the name of the language variable. For example, {LANG_YES} written in the template will show your visitors the word 'yes' if you're using the english language pack.

Whenever you see a {LANG_ in a template, you can look it up at Admin -> Customizations -> Language.

Besides language variables for text, you can use different images for each language and learn how to submit the same listing in multiple languages and have it display in the viewer's language. You may also want to learn how set language via link.