What is an Orthodox Christian?

The Orthodox Church, is the original form of organized Christian religion and was founded at Pentecost (the moment when the apostles first received the Holy Ghost approximately 10 days after Jesus ascended into Heaven) in 33AD.

"When the Day of Pentecost had fully come, they were all with one accord^[a] in one place. ² And suddenly there came a sound from heaven, as of a rushing mighty wind, and it filled the whole house where they were sitting. ³ Then there appeared to them divided tongues, as of fire, and one sat upon each of them. ⁴ And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance." Acts 2:1-4

 For the first few hundred years Christianity was oppressed, we were forced to fly under the radar for our own survival. In fact the first churches were in caves, not the free standing marvels of architecture we see around the world today. 

Once the Emperor Constantine was converted, Christianity became the official religion of the Roman Empire.

Originally there were 5 patriarchates, or hubs of Christianity, they were Antioch, Rome, Alexandria, Jerusalem, and Constantinople. The patriarchates were one in doctrine and morality and stood unified for over 1000 years. Then in 1054 Pope Leo IX declared himself  the infallible and universal head of the Church, an authority that up to this point had never been claimed by a mortal man. This, among other issues, tore the church apart. Leo excommunicated the patriarch of Constantinople for refusing to go along with this and other heresies and was excommunicated by him in response. Though I personally think that Leo expected the other 3 patriarchs to follow Rome (which would explain why Roman Catholics think that we split off from them) they did not and Rome was on its own from that day forward. Those who remained in communion with the other 4 patriarchates came to call themselves Orthodox.

The word Orthodox literally means "Right Glory" though it can also be translated as "Right Belief". I prefer the "Right Glory" translation when discussing Orthodox Christianity because when one uses the "Right Belief" translation there is another word that goes right along with it; Orthopraxy, literally meaning "Right Practice" or "Right action" and Orthodox Christianity asks both of mankind. "Right Glory" is both Right Belief and Right Action.

To be an Orthodox Christian, one must live in the world but not be so sucked in as to be of the world. One must base their opinions on scripture, justice, and the peace of their own conscience; not societal norms and ideals or political loyalties. It is to not judge a neighbor but instead try to understand them, to lead by example instead of coercion and force, and fight sins within ourselves first, fight the situations driving our neighbors into sin next, and to walk upright in righteous, humble, grace where others do not. To do as Christ did, to fight sin and injustice with peace and righteous influence all of your days.