Well, for starters, the statement "The difference between Catholic and Christian" implies that Catholics are not Christians. Sort of like saying "What is the difference between left and right?" Obviously, one is not the other...left is not right, and right is not left. But you may not have meant to word it that way, and that's fine!
The difference is between Catholic Christians and Non-Catholic Christians. There are many. It is much too hard to say what the differences between Non-Catholic Christians and Catholic Christians is, because there are many different beliefs between non-Catholic Christians to compare fairly unless we assume that all non-Catholic Christians go to churches that teach the same as the next. Obviously, there are Baptists, Presbyterians, Pentecostals, Methodists, Lutherans, Episcopalians/Anglicans, and so on and so on that differ between each other on several points of faith, so we can't simply lump them all into one group and compare them to the Catholic Church without explaining the difference between Lutherans and Anglicans, or Methodists and Baptists, or Pentecostals and Presbyterians.
And on that note, by definition, Lutherans and Anglicans can and often do apply the term "catholic" to themselves, though I suspect that by Catholic, you meant Roman Catholic. That being said, the term catholic comes from Greek words that say kata holos, which means "according to the whole." From this, we get katholikos, meaing "universal," which then leads to our modern usage of catholic. Something catholic is universal, meaning it is common to all, or appropriate for all. In the context of Roman Catholicism, considering these to be Catholic Christians, we can see that the name Catholic means a form of Christianity common to and appropriate for all according to it's own namesake. The Roman rite is the most prevelant form of Catholicism and is considered the most universal rite for the whole Church, though there are several others. The term rite, though, means the way in which God is worshiped liturgically. The Roman rite originated in the Roman empire in Rome!
As for the differences between Catholic Christians and other Christians, well, there are many threads in the Bible discussion forum dedicated to the subject, but as a Catholic myself, I would hope you would read the threads along with other scholarly sources such as books. The best way to understand the differences are to ask Catholics themselves what they believe and why they believe it, and ask other Christians what they believe and why they believe it. Don't let a Catholic tell you what Pentecostals believe, and don't let a Pentecostal tell you what Catholics believe. Everyone has an agenda!
Peace!
