Closing a survey means you will permanently stop collecting data on the questions on the survey. However, if later, you decide you would like to reopen the survey, this can be done by going to 'Surveys' > click on the three vertical dots on the right-hand side > 'Resume'. Then go to 'Timing' and adjust the time of the survey of when the next time the survey should launch. The survey would then be open to launch on the designated date of the next round.
Alternatively, you can resume the survey by clicking on the relevant survey > click on the gear logo to open up settings > 'Actions' > 'Resume'.