I'll take a crack at that one, IP.
You might also be surprised to find out that Muslims recognize many people from the Bible.
The name "Christian" was first used among the citizens of Antioch, more as a nickname for the followers of Christ. It seems to have stuck.
Catholics accept a great many things are a part of their doctrine that are not Biblical. While Christ is the central figure in Catholicism, there is also a pope, a particular group of former humans known as
saints who have been identifed and set aside for special consideration and prayer, along with the veneration of Mary as someone who has importance beyond being the mother of Jesus. There are special rituals, not mentiojned in the Bible, which have come to be accepted by Catholics as required for participation by the faithful. This is what is called a "works based salvation." In other words, if you pray the right prayers and fulfill the requirements of attendance, ritual, and doctrine, you achieve salvation.
People who call themselves "Christian," on the other hand, base their faith instead entirely on the Messiah, Jesus, and the saving grace He taught in the Bible, specifically the New Testament, and the principles of the Old Testament that He brought foward into the New Covenant. Christians believe that the references in the Bible to "saints" refers to all believers who have trusted Christ for salvation.
Almost nothing in Catholicism, except the last supper (of course this includes the crucifixtion and all of the characters mentioned in the Bible) is Biblically based, and even then, the doctrine of transubstantiation is not Biblical, either. Christ used the elements of bread and wine as a method of
remembrance of Him. Christ taught that He was the only way to The Father, and that He and the Father "are one." Christ Jesus is the Messiah mentioned in the Old Testament, and He fulfilled all of the scriptural tests for His identity to be clear. Only by being "born again" by faith in Christ, according to the Bible, can one be saved.
Acts 4:12 says:
"Nor is there salvation in any other, for there is no other name under heaven given among men by which we must be saved."
Not Allah, not Mohammed, not Krishna, nope, "no other name."
So, to sum up, Christians follow doctrine from Christ in the Bible, and Catholics follow additional doctrine that is not in the Bible.
I hope this helps to determine the difference in beliefs for you.