Navigation buttons are on the bottom right corner of the screen and it helps respondents navigate up and down in the survey. You can use the up button to go back to the previous question and the down button to go to the next question. You can enable or disable the navigation button by accessing Show Navigation buttons.
This is how it would appear to the respondents if the Show Navigation Buttons are enabled
This is how it would appear to the respondents if the Show Navigation Buttons are disabled