The invention of a reliable and versatile printing press by Johannes Gutenberg in the mid-15th century heralded a new era in communication. The printing press greatly enabled the Reformation in Europe to gather momentum and disseminate biblical teaching widely.
Although distributing Christian material pre-dates the printing press, this invention certainly facilitated many more having access to biblical truth through Scripture portions and tracts.
A tract is a short piece of evangelistic literature. The value of printed tracts with the express aim of communicating the gospel was soon realised by leading Christians of their day.