Although both Protestants and Orthodox are Christians, there are many differences between their beliefs. One of the key points of differentiation for the two groups is how they each understand the relationship between the Bible and tradition.
The Orthodox believe in something called sola scriptura, which translates to "scriptures only." Essentially, their belief is that Christians should follow only what has been written in the holy scriptures and nothing else. To that end, the Orthodox believe solely in the teachings of the Church, as they believe it is the safeguard of truth on earth. Many adherents of Orthodoxism focus more exclusively on just the New Testament teachings that were actually experienced or witnessed by the Apostles firsthand. This is called the Apostolic Tradition.
Comparatively, individuality is more prevalent in the Protestant faith. They believe that the bible has multiple correct interpretations and that each should read it and consider its meaning for herself. This is a stark difference from the teachings of the Orthodox church, which believes that no individual, outside of the Holy Fathers, is qualified to interpret the meaning of the bible. The two faiths view the bible and its teachings in vastly different ways. However, they both believe that Jesus is the son of God who died for our sins.