I am assuming you are genuinely confused about this issue...I may be wrong.
People talk about those who are what they call "nominal Christians" . These are people who maybe go to church at Easter, or for a Funeral and believe that if you are a good person, try to do unto others as you want them to do for you, then you will go to heaven. These same people may cuss and swear, drink beer a lot, even take the name of Jesus in vain a lot....but they will tell you that they are Christian.
Others think that if you are white and descended from the British Isles that you Christian.
Of course the Bible should tell us what a Christian is.
The only time the word Christians is mentioned in the Bible is in the book Acts.
Act 11:25 Then Barnabas departed for Tarsus to seek Saul.
Act 11:26 And when he had found him, he brought him to Antioch. So it was that for a whole year they assembled with the church and taught a great many people. And the disciples were first called Christians in Antioch.
Previous to Barnabas and Saul(Paul) preaching and teaching the disciples in Antioch Luke tells us this...
Act 11:20 ...when they had come to Antioch, spoke to the Hellenists, preaching the Lord Jesus.
Act 11:21 And the hand of the Lord was with them, and a great number believed and turned to the Lord.
So these ones that were called Christians by those in Antioch...were disciples or followers of Jesus...having had Jesus preached to them....by which they had been enabled to believe the Good news about Jesus by the hand(power) of God. God also enabled these Antiochans to leave their old ways of idolatry behind and to TURN (repent)to Jesus the LORD.
It tells us that first of all, a person needs to hear the good news of Jesus Christ...
Hear Paul's preaching...
I declare to you the gospel which I preached to you, which also you received and in which you stand,
1Co 15:2 by which also you are saved, if you hold fast that word which I preached to you—unless you believed in vain.
1Co 15:3 For I delivered to you first of all that which I also received: that Christ died for our sins according to the Scriptures,
1Co 15:4 and that He was buried, and that He rose again the third day according to the Scriptures,
The Antiochans had Jesus preached to them....
They believed and turned to Him
He became their LORD AND SAVIOUR.
They would have been baptised in water in the name of Jesus
They would have received the infilling of the Holy Spirit
Thus they were enabled to love God and love all people
So they now were like Jesus Himself
Thus they were called Christians-- LIKE CHRIST.
What makes one a Christian?
God does it, by granting us faith in Jesus Christ and repentance/turning to Him away from other gods and power to live as Him in this world.