Who uses structured interviews?
Government employers describe them in detail. The US Office of Personnel Management's page on structured interviews says they are usually scored by a panel, with each member rating responses individually before a group discussion. It says interviews with more structure show "higher levels of validity, rater reliability, rater agreement."
In Canada, Health Canada's guide to acing the interview says Public Service interviews usually follow "a fairly formal structure." Candidates are assessed against the Statement of Merit Criteria, often by a board of two or three people.
What does a structured interview mean for your answers?
Each answer is rated against benchmarks of proficiency, so treat every question as its own small test. Cover each question's point directly and give a specific example. OPM's FAQ on structured interviews says all interviewers must reach consensus on the ratings.
Where can you read more?
The guide on how interview scorecards work shows what interviewers fill in. The guides to behavioral interview questions and panel interview tips cover the question types and the format. The glossary entry on behavioral vs situational interviews explains the two common question styles.