I wanted to add a few details to the excellent answers to date. One point I did not see mentioned is that the hiring committee who reviews the collective interviewers feedback not only gets a score but also a complete write-up of the course of the interview from which they can draw their own conclusions. In addition they see the histogram of the scores an interviewer has given out to other candidates so they can weigh the relative experience level of the interviewer and whether they tend to assess candidate’s easier or harder than average. When learning to interview we also get to see what our peers said about the same candidate which helps us to self-correct our expectations.