The most important element is Christianity is Jesus. Christians believe that Jesus is the fully divine, yet fully human representative of God on earth. He came to Earth roughly 2000 years ago to live, minister, die, and then resurrect from the dead. (John 3:16) "For God so loved the world that He gave His only begotten Son that whosoever believes in him shall not perish but have eternal life." Through this transaction of accepting Jesus' life, death and resurrection, a person can exchange his/her sins, iniquity, and damnation for righteousness, hope and eternal life. This is the basic foundation of Christianity.
Jesus then instructs Christians, through the teachings to his disciples, how to love God and how to love others.