Did Gutenberg invent printing?
No — printing existed for centuries before him in East Asia. What he invented was a system that made printing with movable type economically transformative in Europe, which is a narrower and more interesting claim.
What existed already:
Woodblock printing in China from at least the seventh century, producing complete printed books centuries before Gutenberg.
Movable type in China, developed by Bi Sheng around 1040 using ceramic type, and later in wood and metal.
Metal movable type in Korea, where the Jikji was printed in 1377 — roughly 78 years before Gutenberg's Bible — and is the oldest surviving book printed with metal movable type.
Why movable type mattered less in East Asia. A script with thousands of characters makes individual type enormously expensive to produce and store, while woodblock carving of a whole page is comparatively efficient. The technology was not superior for that writing system, which is the substantive explanation and not a deficiency.
What Gutenberg actually contributed, which was a combination rather than a single invention:
A type-casting system — a hand mould allowing rapid production of identical, interchangeable pieces of type in quantity, from a metal alloy of lead, tin and antimony that cast crisply and wore well. This is the genuine innovation, and it is a metallurgical and manufacturing one.
An oil-based ink adhering to metal type, where existing water-based inks did not.
An adapted press, derived from wine and olive presses.
A workable commercial process integrating all of it.
Why it transformed Europe specifically. An alphabet of a few dozen characters makes movable type overwhelmingly efficient — the economics that failed in East Asia succeeded in Europe.
What followed: an enormous fall in the cost of books, mass literacy over time, the Reformation's spread, standardisation of vernacular languages, and the scientific revolution's communication infrastructure.
Gutenberg himself lost his business in litigation with his financier and died without wealth.