What is a Christian?

A Christian is someone who

has repented of sin

and has been baptised in the Name of Jesus,

who then receives the forgiveness of sin

and receives the Holy Spirit, who then inspires and empowers him

to be obedient to God for the rest of his life

and follow Jesus, even to the point of death if that is necessary.

This is what I read in my Bible in Acts 2:38

Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.