It contains the entire common part of the Holy Mass in the Extraordinary Form, also known as Tridentine Mass, together with its translation into English. It is, therefore, the part of the Mass that the faithful will hear repeatedly in every Mass, and is consequently the part which should be learned, and its meaning understood, better than any other.
It also teaches what the believer has to say, their posture at all times, their gestures (such as tapping chest or crossing oneself) that must be carried out. Also the gestures made by the priest, his changing volume of voice...etc.
A detailed Ordinary of Mass for anyone who wants to better know and understand this Mass. We could say that it is the detailed and precise description of the greatest divine work of art.