A structured interview
(also known as a standardised interview or a researcher-administered survey) is a quantitative research method commonly employed in survey research.
Structured interviews are a means of collecting data for a statistical survey.
A structured interview also standardises the order in which questions are asked of survey respondents, so the questions are always answered within the same context.

Unstructured Interviews are a method of interviews where questions can be changed or adapted to meet the respondent's intelligence, understanding or belief. Unlike a structured interview they do not offer a limited, pre-set range of answers for a respondent to choose, but instead advocate listening to how each individual person responds to the question.