I alwas wanted to know what is different because I know we both believe in the same God, read the Bible,believe in Jesus Christ, etc.

I'm not sure, but as far as I know from history courses, all people, who believe in main aspects of Christianity are called Christians. But Christians are separated to a kind of "sub-teams". Each team beliefes differs from the others, because they pick and believe only a few parts of the main aspects of Christianity(don't ask me what's the main aspects of Christianity, because as an Orthodox, I'm biased about the answer). So Catholics, are one of those sub-teams of Christianity, in my mind.
I think those "sub-teams" created during the last days of the roman-byzantine empire, because the empire was almost divided and there wasn't lots of coherence among the different nationalities, which used to consist that huge empire.
If you know more about this historic view, that I tried to express, feel free to add or omit something about my opinion. As I said, I'm not so sure about this topic.

Catholicism is a branch of Christianity, there are many branches of it, such as Baptists, Episcopalians, Protestants (mind you this is just a small example), many man religious ideas have off branches, like Judaism has orthodox and nonorthdox followers.

They all have the same basic religion but worship differently.

My point is, Christianity is pretty much the worship of God and Jesus, and most Religions that do that as well.

Jerkerz : There is no right style of worship. However, there is a right kind of worship. Catholics are Christians in the sense that they believe in salvation through Christ, but there are several major differences between the two. Below are 2 short articles that I believe accurately explain the differences.

http://www.gotquestions.org/Catholic-Biblical.html

http://www.gotquestions.org/difference-Catholic-Protestant.html

The Catholic church is different in the key theologies in Christianity.

Here is the thread that I posted, talking about some of the points in Catholicism that are not Biblical, which shows that those who follow Catholic theology are not Christian:
https://www.vizzed.com/vizzedboard/thread.php?id=13009

The difference is that Christianity is of God and Catholicism. Examples of it not being Biblical are that you call the priest father, the fact that they hold angels in such high reverence, and that they pray to Mary, and probably the most well known example, purgatory.