In our internet age filled with email, texting and tweets, it's hard to imagine that up until the invention of the printing press in the mid-15th century, each individual page of every book that existed on planet Earth was a unique, hand-rendered work of art. When copies of a particular book were needed, the book had to be borrowed from somewhere and painstakingly rewritten, word for word, by hand. The term "manuscript" itself means written by hand. Obviously this kind of close, exacting work was tedious and physically tiring, as any grade school child who's ever had to write out "I will not talk in class" one hundred times on a blackboard or notebook paper can testify.
Producing copies of the Bible and other books for liturgical use by monasteries was the principal focus of early manuscript production. Large, beautifully decorated books were also wanted for use by Christian missionaries in evangelization. Catholic monasteries throughout Europe took on this work by creating highly productive scriptoria, or writing rooms, where monk scribes toiled many hours a day, often in cold and very austere conditions, to create the needed books.
Creating and copying religious books was only a part of the monastic contribution to learning and literacy throughout the Western world. Many monasteries also took on the heroic work of copying and preserving the great pre-Christian Greek and Latin intellectual works of antiquity, most of which would otherwise have been lost to us forever. Repeated barbarian and Moslem invasions in the middle ages destroyed countless monasteries and killed a great many monks, but ultimately would not stop the forward progress of Western civilization led by the great monasteries. We owe a tremendous debt of gratitude to the Church throughout this time as a leading innovator in science, law, agriculture, education and literacy, architecture, art and music, and for the creation and preservation of countless manuscript masterpieces.