Hi Awesomeee,
The Catholic Church was the original Christian Church. Martin Luther disagreed (protested against, hence protestant) with some of the things rhe Church was doing, such as inventing purgatory and intinerant priests going around and selling indulgences, getting people tp pay money to get their deceased loved ones released from purgatory. He had other things he objected to , but I don't remember what they were. He broke off from the Church beginning the Protestant Reformation when he nailed his 95 Theses to the door of the Church in Wittenburg, Germany in 1517. Other protestant denominations arose from the original potestants, Lutheran, Calvinisrs, Puritans, and later, lots of others.
Henry VIII of England also broke away and started the Church of England because the Catholic Church wouldn't aloow him to divorce Catherine of Aragon and marry Anne Boleyn. He set it up with the King being the head of the Church of England.
Anyway, Catholics are Christians, but there are many other Christian denominations as well.