Protestant refers to a branch of Christianity that originated in the 16th century during the Reformation, a movement aimed at reforming the practices and beliefs of the Roman Catholic Church. Key figures, such as Martin Luther and John Calvin, challenged the authority of the Pope and emphasized the importance of scripture and faith in salvation. Protestants are characterized by their belief in the priesthood of all believers, meaning that individuals can have a direct relationship with God without the need for a priest. This branch of Christianity includes various denominations, such as Baptists, Methodists, and Lutherans, each with its own interpretations and practices.