As recorded in the title, the Douay-Rheims version is a translation primarily from the Latin Vulgate.  A brief selection from the preface to the 1582 edition explains the reasons for this approach.  Together with the glossary the text shows the translators scholarly motivations, but also provides a glimpse into the charged climate of the period.  The transcriber hopes he did a tolerable job in transliterating the Greek words in the preface.  The glossary contains words newly used in the language of the day.  Some were later dropped from the Challoner revision, others have found common usage today.