The printing press created by Johaness Gutenberg revolutionize the printing process. The printer was had two different characteristics; the wooden frames and the movable metal letters. The metal letters themselves accelerated the printing process on a large scale because it made a precise are rapid production.
It's hard to understand the revolutionary creation that the printing press was if we compared that type of production we have now a day's with digital printing. Before the printing press arrived there was the Woodblock printing, a completely manual way of printing (Someone would carve wood and create a "stamp"). After the woodblock, the movable type was created (it was the same idea but the letters would be industrially made of porcelain, making easier to write words).
The printing press idea of metal movable letters made a faster way of writing and therefore, a faster way of printing. As a result, the printing press reduces the cost of printing books and other documents.