Christianity is a relationship with the true and living God through the person of Jesus Christ by whom we are forgiven of our sins. Without Jesus, a person is separate from God and cannot no relationship with Him. Ephesians 2:12-15 says:
...remember that you were at that time separated from Christ, alienated from the commonwealth of Israel and strangers to the covenants of promise, having no hope and without God in the world. But now in Christ Jesus you who once were far off have been brought near by the blood of Christ. For he himself is our peace, who has made us both one and has broken down in his flesh the dividing wall of hostility
So fundamentally, Christianity is a relationship with God. Is Christianity also considered a religion? It depends on how you define religion. If you define religion the way Wikipedia has defined it, a religion is a set of beliefs concerning the cause, nature and purpose of the universe, especially when considered as the creation of a supernatural agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs, then yes. Christianity is based on the teachings of Jesus Christ, so it is a faith system or a religion according to this definition. However it is NOT a religion if we define religion as a set of rules one must follow to gain salvation or to earn God's favor. In fact, Christianity stands apart from all other belief systems because it teaches salvation by GRACE. All other systems tell us we must do certain good things in order to be in God's presence. Christianity tells us we are not made right before God by our efforts, sincerity, or works. Instead, we are made right before God by faith in what Christ did on the cross.
[Answered by Pastor HM]
Reference: "What is Christianity" by M. Slick
