This book is in two parts. The first is a brief explanation of the Holy Sacrifice of the Mass. The second is a guide to those who are new to Catholic apologetics and need some answers when trying to defend the faith. In the first part, when one reads a definition of Mass it is usually: Mass is the unbloody sacrifice of Calvary. But what does it mean and why is Mass like Calvary? What is it a sacrifice and why do we call Mass the Holy Sacrifice of Mass? Also, one often wonders if they have to pay attention to what the priest is doing at the altar. The idea for the second part came about for many reasons. The most important of these are after close contacts with a Protestant group whom I found swept up in the ideas of private interpretation of the Bible and the belief that they are part of the true church of Christ. Often when I show them that their interpretations are wrong and what the correct ones are they defend their beliefs saying something like "the Holy Ghost inspired me therefore how can I be wrong?" Now is the time to understand and defend the faith. It is with great hope that this book will help you do so.