A Christian is a person who accepts and seeks to follow the teachings of the Lord Jesus Christ. That means that Catholics, Orthodox, Protestant, Latter-day Saints, Christian Science, and Jehovah Witnesses are Christians.
Now members of these very broad groups do not believe the same things. Many would not consider members of the other groups to be “true” Christians. But each would consider themselves to be real Christians.
Are They Saved
A second question, is what does it mean to be saved. This is more complicated, because it requires us to interpret Scriptures and list criteria. I can only answer that from my own belief system.
Salvation
A person is saved if and only if they have turned from a self-centered life to a God-centered life through repentance and faith in Jesus Christ as Lord, Savior, and God. Let me unpack that.
Conversion, in my view, is turning from a self-centered life to a God-centered life. This is also the core idea of repentance, a change of mind. The change is from loving self first to loving God first.
Faith is trust. You must place your trust in the person of Jesus and accept what he did for you on the cross. He died for your sins so that God can forgive you and give you citizenship in his kingdom. And unless Jesus is somehow God in the flesh, none of this makes sense.
Now how all this is possible is part of the Christian Community’s struggle to understand the gospel and apply that to our lives. It is when we reach a collective consensus that a creed becomes authoritive or a canon gets closed. I am simplifying this a lot.
True Christians
Now back to our question. Now if we mean by true Christian one who is also saved, then members in each one of these groups will have Christians who are saved and Christians who are not saved. This is exactly what Jesys taught:
“Let both of them (saved and unsaved) grow together until the harvest, and at harvest time I will tell the reapers, Collect the weeds first and bind them in bundles to be burned, but gather the wheat into my barn” (Matt. 13:30).