Exit link is used to place an exit button in each question of the survey. You can disable or enable the option from Survey Setting options. This would allow the respondents to exit the survey at any point without having to close the survey manually. You can set the Exit Link URL from the Completion Rule in the Advance section.
This is how it would appear to respondents if the Exit Link is enabled.
This is how it would appear to respondents if the Exit Link is disabled.