Key Concepts - Christianity

1.Trinity: The Christian doctrine of the Trinity  defines God as three consubstantial persons, expressions,  the Father (God), the Son (Jesus Christ), and the Holy Spirit ("it is the Father who generates, the Son who is begotten, and the Holy Spirit who proceeds"). According to Christian theology, God can only be recognized through the holy trinity. 

2. Incarnation: The belief that the second person of the trinity (Jesus Christ) was given flesh through the womb of Mary. He is recognized as both man and god. It is celebrated through the holiday Christmas. 

3. Church: A building used for Christian religious worship. They are often erected in the shape of the cross and represent the body of Christ. They are used for group worship mostly on the sabbath (Sunday). 

4. Salvation: The act of saving the soul from sin. Salvation has been made possible by the life, death, and resurrection of Jesus Christ. Different denominations of Christianity prescribe different ways of achieving salvation. 

5. Kingdom of God: The relationship between God and humanity is called the "kingship of god". God's Kingdom is Heaven. The term is primarily used by Jesus Christ in the first 3 gospels.  The idea of God as king stems from Judaism which predates Christianity. 

6. Atonement: Jesus Christ died on the cross for the sins of man, this sacrifice reconciled us to God. Jesus was able to redeem us from sin, however, the price for this redemption was his life. Jesus described his death as a ransom payment but it is unclear as to who the ransom was paid to. Some speculate that it may have been the devil.

7. Sin: The breaking or transgression of God's law. It can also be defined as the disobedience or opposition to God. Sin came into the world when the serpent, Satan, tempted Adam and  Eve and caused them to disobey God. 

8.  Resurrection: Meaning coming back to live after death, in reference to Jesus Christ dying on the cross and resurrecting 3 days later. His resurrection allowed for the salvation of man. 

9. Redemption: Forgiveness or absolution for past sins. It provides protection from damnation. It can also mean freedom from captivity. 

10. Repentance: The stage in redemption in which the believer turns away from sin. Some believe it occurs prior to faith and others believe that it occurs after faith. It acknowledges that you have done something wrong and that you feel remorse for said action. 

http://www.patheos.com/blogs/christiancrier/2014/08/28/what-is-the-bible-definition-of-church-what-is-the-biblical-view-of-church/

http://en.wikipedia.org/wiki/Salvation_%28Christianity%29

http://www.britannica.com/EBchecked/topic/236611/Kingdom-of-God

http://christianity.about.com/od/glossary/f/whatissin.htm

http://en.wikipedia.org/wiki/Repentance_%28Christianity%29