What is Christianity?

Christianity is:

1. Christ gathering for himself those whom God has given Him.  John 17:9 - I pray for them. I am not praying for the world, but for those you have given me, for they are yours.
2. Christians, once having been justified by His grace and under the new covenant, continuously depend on his power inside us, to become a fully grown members of His body. Heb 8:10b - I will put my laws in their minds and write them on their hearts. I will be their God, and they will be my people. 

Keep in mind, He put "everything in us" to become fully grown parts of His body. We can encourage each other, speak His word with each other in love, love each other, disciple each other but not teach (literal day to day coaching) each other. Why? That is not our job and is Holy Spirits Job and Shepherd's job. Heb 8:11 - No longer will they teach their neighbor, or say to one another, 'Know the Lord,' because they will all know me, from the least of them to the greatest.