It means that when he speaks on matters of faith and morals in his office as teacher of the universal Church, whether speaking «ex cathedra» or in
the ordinary exercise of his office, he is guaranteed to speak free from error by a special outpouring of the Holy Spirit.
As a general rule, a participant expert with special skill, knowledge, training, or experience may give opinion evidence without complying with r. 53.03 where (i) the opinion to be given is based on the witness's observation of or participation in the events at issue and (ii) the witness formed the opinion as part of
the ordinary exercise of his or her skill, knowledge, training, and experience while observing or participating in such events.