When distributing a survey project to your community/panel, this option helps you select any of the languages you have added to the Survey at Edit Survey > Languages. On clicking of the survey link provided in batch mail send to Community Member the survey will get open in the language you selected at the time of distributing your survey.
When distributing survey to your community, on select of survey all the languages associated with your survey will be available in a drop down. Just select any language of it and Send the invite to Community Members. This will open the survey in selected language while responding.
This feature is available with the following license :