Why do some questions have square buttons while others have circles?

Closed-ended question types will either have circular radio buttons or square checkbox buttons, depending on the question settings. The shape of the button determines how many answer choices a respondent is allowed to select.

Radio Buttons:

Radio buttons indicate that respondents can only select one answer from the list of choices. When a respondent selects an answer choice, all other answer choices are deselected automatically.

Checkboxes:

Checkboxes indicate that respondents are allowed to select multiple answers from the list of choices.

On questions that allow multiple answers, you can set a range or a limit on how many choices respondents must select. Learn more: Making Survey Questions Required