The Protestant Reformation was a Christian reform movement in Europe which is generally deemed to have begun with Martin Luther's Ninety-Five Theses although a number of precursors such as Johannes Hus predate that event. As a historical period, the Reformation is considered to have ended with the Peace of Westphalia in 1648;however, many of the denominations that arose during that period continue to exist and Protestantism constitutes one of the branches of Christianity today.
Martin Luther nailed a letter to the roman Catholic church door to protest the churches control of the people . He thought people were capable of making their own spiritual decisions. In effect they should live by faith in God, not just blind faith in the church. These Protestants were born from such protests.
Well, the "standard" answer is "Protestantism," but that is WAY too broad to be meaningful. Lots of local congregations or groups of affiliated congregations consider themselves "Protestant," but are not particularly linked with the Reformation Movement...
Also, there had been numerous attempts to "fix" the "broken" catholic system for a little over 1000 years before the "movement" is generally considered to have begun.
Look up, for instance, the "Lollards," a group based in England in the 14Th century, long before Martin Luther "defaced" the chapel door in Wittenberg. This group seems to have been largely responsible for the first complete English Bible, Wycliffe's translation, completed around 1385... BEFORE the invention of Gutenberg's printing press, so they were all hand copied.