Protestant refers to Christians who belong to churches that broke away from the Roman Catholic Church during a period called the Reformation, which began in the 1500s.

A German monk named Martin Luther sparked the Reformation in 1517 when he questioned whether people could buy their way into heaven and argued that the Bible, not the Pope, should be Christianity's highest authority. His ideas spread rapidly thanks to the recent invention of the printing press. Other reformers like John Calvin in Switzerland and King Henry VIII in England led similar movements, each creating different Protestant traditions.

Today, Protestants include Baptists, Methodists, Lutherans, Presbyterians, Anglicans, and many other denominations. While they differ in worship styles and specific beliefs, most Protestant churches share some common ideas: that people connect with God through personal faith, that the Bible is the ultimate religious authority, and that church services should be conducted in people's everyday languages rather than Latin.

Protestants and Catholics are both Christians who believe in Jesus Christ, but they have different traditions about how churches should be organized and how people should worship. Understanding these differences helps make sense of European and American history, since conflicts between Protestants and Catholics shaped wars, migrations, and the founding of colonies for centuries.