The term “Christendom” as used on this web site is referencing a group of people that claim Christianity as their belief system. This would include all individuals and churches that are part of the Eastern and Western traditions of the ChristianAccording to the Bible, Christians are those that put their faith in Jesus Christ and follow him as Lord and King of their lives. To reject that Jesus is not equal in nature with God or reject the teaching of the Trinity of God would forfeit anyone's claim to be called Christian. (Acts 11:26, 26:28;... church.