The world’s largest religion, Christianity brings meaning to the lives of about 2.4 billion adherents.  It is a monotheistic religion based on the life and teachings of Jesus Christ. It is the prevailing and iconic religion of the Western world.
There are three major branches of Christianity: Catholic (50%), Protestantism (37%), and Orthodox (12%).  It should be noted that “Christianity/Christians” is an umbrella term that incorporates a stark diversity of faiths.Although the global percentage of Christians has hovered around 33% for the last century, there have been some large shifts: Christianity is in decline in ‘developed’ countries and on the rise in the developing world. Protestantism is one of the fastest-growing religions in the world (behind Islam and non-spiritual) and is accelerating (though Catholicism may be in decline). 
Put simply, Christians believe that Jesus is God’s Son, and was sent as the Messiah (savior or liberator) to Earth to save humanity from the effects of sin, as prophesied in the Old Testament.Whether by free will or divine grace, Christian’s believe that salvation is granted to individuals who trust in Jesus Christ, with faith, for the remission of their sins.
Stemming from this exclusivity and its interpretation, and with the varied history of creeds, sects, churches, denominations, etc. there are many paths to calling oneself a Christian, and members of different branches of Christianity often deny that other branches are truly Christian.Catholics may argue that the Luther & co sought to supplant the Christian faith with a new one, while Protestants would argue that Catholicism did so long before, and was in need of reform.
These tenets of belief hold in almost every form of Christianity:
- Belief in God, Jesus as his son, and the Holy Spirit
- Humans were created by God in his image, then tainted by sin and suffering, from which they seek redemption
- Jesus’s crucifixion, resurrection, and ascent into heaven as a holy sacrifice
- Jesus Christ’s second coming to earth, Judgment Day, and ultimate salvation of all faithful souls.
The traditions and expressions following these tenets have birthed countless denominations and branches, making a one-page summary of “Christianity” a hopeful goal indeed. Nevertheless, we’ve gathered a slew of resources for further reading/listening/watching. Dig in, and learn more about Christianity in its many forms.
Here is a fun graphic timeline of Christian denominations. See key below for Wikipedia links. 
Oh, and don’t forget…
- Bible Hub: A fairly academic online Bible (with basically every version) and web of related resources
- Bible Gateway: A Bible-focused site with a search-able archive of many articles and explanations
- Christian Post: As it sounds, global news from a Christian lens
- Got Questions: A popular site answering questions about Christianity. This link leads to their top 20 most frequently asked questions.
- Catholic Answers: “To Explain and Defend the Faith”. This project began in 1979 when its creator wrote rebuttal leaflets responding to misinformation at his church.
- New Advent: World News through a Catholic lens
- Patheos: Link to their portions about Christianity. Like a much more extensive Wikipedia
- Christian Fact Slides: Some fun trivia about Christianity
- Christianity in 2 minutes: Christianity very simplified for anyone who knows very little about the religion.
- What is Christianity in 5 minutes: A similar video to above, but speaks more like a sermon, using a single evolving infographic to explain the spiritual tenets of Protestant Christianity.
- Christianity 101: ~8 min. Similar to the two above, but a bit more depth and more academic.
- Christianity from Judaism to Constantine: a strictly historical look at the world Christianity came from, this video by CrashCourse is great for its densely packed information and super good visuals. Also light-hearted and funny.
- Luther and the Protestant Reformation: supplementary to the last video, another in-depth, funny, and dense history lesson about a pivotal time in Christian history.
- Catholicism 101: ~17 min. a well-spoken radio host explains the catholic faith.
- “Christianity 2015: Religious Diversity and Personal Contact” (PDF). gordonconwell.edu. January 2015. Retrieved 29 May 2015.
- Protestantbranches.svg: Lokal_Profil derivative work: Hogweard