Orthodox Christianity.
1. Assembled the Holy Scriptures. Specificly the NT books.
2. Wrote the Nicene Creed and defined, and continues to define, it's components.
3. Invented the word "Trinity" to describe the God head.
4. Defined the dual nature of Christ, fully God and fully man.
5. The Church of the 7 councils.
Was guided by 5 great elders, known as Patriarchs, through the first 1000 years of her existance. The Patriarch at Rome was the first among equals among the Patriarchs, but there was no one Patriarch that ruled over the entire church.
There was a division between the Roman Patriarch and the other four in 1054. From that date to now, we have Eastern and Western Christianity.
To this day we use the liturgy of St. John Chrysostom and St. Basil. We also have the liturgy of St. James, but is rarely, if ever, used. This liturgy is where we partake of the body and blood of Christ. We call it by it's Greek name, Eucharist (transliterated, of course). We believe that by the power of the Holy Spirit, the bread and wine ARE the body and blood of Christ. We do nor seek to define how this is done.
We have various other offices (services) designed to keep the faithful on track. These include Matins, Vespers, and Compline.
We believe that salvation is a process, not a singular event.
We believe in a sacremental life. And a life of repentance.
For most of us, we worship standing up. We also do not use musical instruments in worship. (But this is not a canon law)
We call our pastors priests, a mis-shappen form of presbyter. We call him "Father," as he is our spiritual guide, just like a biological father. Similar to Paul's relationship to Timothy, whom he considered a son in the faith.
We include the entire church in our worship. That is, we do not exclude those who have quit breathing oxygen. We ask those who do not need air to pray for us, just as we would as those who need air to do the same. (This, BTW, includes Jesus' mother, Mary)
We have, and kiss, pictures of the precious defenders of the faith. We keep their memory alive among us by keeping their images before us. In addition, we keep their images to remind us that we too can live holy lives.
We consider the Holy Scriptures to be the greatest of written Tradition that belongs to the church. We bind it in gold. We carry it among the peoples at our services. We kiss it. But most importantly, we read it. Close to 75% of all our services are scripture being either read or prayed.
There's so much more. But this should get you started.
Peace.
Peter