The Reformation, also known as the Protestant Reformation, was a series of events in 16th-century Europe.
The reformers challenged the authority of the Catholic Church. Eventually, Western Christianity split into Protestantism and Catholicism.
Although they have much in common, Protestant and Catholic churches differ in many aspects of teaching and practice.
The Reformation started when Martin Luther, a monk in what is now Germany, published 95 complaints against the Church. Luther was banished from the Church and his ideas officially banned.
In general, the Reformers argued that salvation in Christianity can come from faith in Jesus. This differed from the Catholic view that salvation requires good works.
While the Catholic Church used Latin as the language of public worship, reformers translated the Bible and other texts into more languages so that ordinary people could read them.
Text adapted from English Wikipedia, Creative Commons Attribution-ShareAlike License 4.0.
Ferdinand Pauwels: English: Luther hammers his 95 theses to the door, painting 1872, via Wikimedia Commons, Public Domain.