A structured interview is one where every candidate for a role is asked the same core, job-relevant questions and scored against the same defined criteria. It sounds obvious, but it is the opposite of how most interviews run, which is a free-form conversation where the questions are made up on the spot and the outcome is a general feeling.
The reason structure matters is that it is one of the strongest predictors of job performance, well ahead of the unstructured chat. Asking everyone the same questions makes candidates genuinely comparable, because they answered the same things. Scoring against clear criteria, ideally before the panel discusses anyone, keeps the loudest voice or the strongest first impression from deciding the outcome.
Structured does not mean cold or scripted. Interviewers can still follow up and go deep on individual answers. It simply means the backbone of the interview is consistent and tied to what the job actually needs, so the decision reflects evidence about the work rather than chemistry in the room. It is also far easier to defend later, because every judgment rests on the same criteria.