The Protestant Reformation of the 1500's caused a significant split in the church with many choosing to leave the organized Catholic church and plant various other "Protestant" churches.
Martin Luther is widely accredited with starting the Protestant Reformation with his "95 Theses" which he nailed to the door of the All Saints Church in Wittenberg on October 31, 1517. (Next year is the 500th aniversary) This document, composed in Latin, challenged the Popes authority and the churches selling of indulgences among other things.
Luther's attempt to reform the Catholic church led to his excommunication and separation from the church and ultimately the creation of a new kind of church called the Protestant church. The Protestant movement has led to many different denominations including but not limited to Baptists, Anabaptists, Calvanists, Lutherans, Methodists, and Pentacostals.
Many popular church denominations today have originated from this Protestant movement and still hold to the positions that Luther and others like him espoused.
The Catholic church has resisted many of the changes that Luther recommended and has held to the many of the original traditions and practices but both groups have evolved slightly over the years.
This massive split within Christendom has led many people to ask, Who's right? Is Catholicism a truer expression of Christianity than Protestantism? Are Catholics even Christian? Are Protestants? If I choose to follow Jesus, will I be better off following him in a Catholic church or a Protestant church? Does it even matter? What are the actual differences between the two?
If you have questions about Protestantism or Catholicism, you are in luck. Pastor Brian Reed gave a seminar which you can listen to here. Also feel free to follow along with the downloadable notes.