Basically it facilitate the rapid production of multiple copies of various and sundry materials. It is said that th epope at the time specifically stated that if the Bible was in the common languages of the people that the catholic church would be ruined - prior to the printing press, it was only in Latin in Europe.
The Catholic church fought the printing press as a tool of the devil. Gutenberg encountered financial problems and had to sell his invention to a many named Foust. The Catholic Church, to promote their concept that the press was the tool of the devil, equated Mr. Foust to Faustus, the character in a medieval story where a man named Faustus sells his soul to the devil.
The press made it possible for men like Erasmus, Thomas More, Martin Luther, Huldrych Zwingli, and Calvin to get their materials in front of people much faster and would have been, therefore, instrumental in bringing the Reformation about much earlier than it otherwise may have been.