Pope Francis and Republican presidential candidate Donald Trump do not see eye to eye regarding the latter's Christianity since the pope believes that Christians would not close their hearts out on immigrants.

For American evangelist Franklin Graham, on the other hand, it is easy to understand who or who is not a Christian. "There has been a lot of talk the last couple of days about what it means to be Christian. Simply put, a Christian is a person who is a follower of Jesus Christ," he writes on his Facebook page.

Even though Graham was raised by loving Christian parents—world-renowned evangelist Billy Graham and his wife Ruth—he did not truly become a Christian until he was already 22 years old. It was only then that he "asked God to forgive me of my sins and I put my faith and trust in His Son Jesus Christ. I invited Jesus into my heart and turned my life over to Him—and I've been following Him ever since."

"Being a Christian has nothing to do with being a Presbyterian or a Baptist or a Catholic—religion can't save you," he adds. "You have to confess your sins, turn from your sins, and believe in Jesus Christ, who took your sins to the cross, died, was buried, and God raised Him from the grave. That's the Good News, that's the Gospel."

Graham then shares two Bible verses about Christianity. The first is from 1 John 4:10, which reads: "This is love: not that we loved God, but that He loved us and sent His Son as an atoning sacrifice for our sins."

The second verse is 1 John 1:9, which states that: "If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness."