Usually, in panel interviews, the panel members will take it in turns in asking the questions. On occasion, the panel may also ask some on the spot questions depending on how the candidate responds.
Due to there being more than one interviewer, there is more accuracy and clarity with this process. As most of the questions are the same, conducting this style of interview allows the interviewer to hear a range of different perspectives on the same topic. Due to this reason, it makes it easier to compare the candidates and finding the right candidate is faster.