And while we're on the subject, could someone please sum up the difference between Catholics and Christians in about 1 or 2 lines? I've never really understood.

I'll put in my understanding here. I hope it helps. But I never seem to be able to write anything in 1 or 2 lines. (If you must have it that short, though, simply read the two bolded phrases).

First of all, it should be noted that Catholics ARE Christians (though Protestants sometimes debate the title). The proper deleniation is between Catholics and Protestants (though technically I think the Anglican church is not considered Protestant since it did not come out of the reformation). The Catholic church is the historical church and grew out of the early Christian movement. The Protestant Churches split off later over two main issues. These two issues remain the main source of contention today:

1. The Authority of Scripture. The Catholic church maintains that only the Church may intepret scripture, and that the traditions of the church are equal in Authority to the Bible. Protestants believe that interpretation is a responsibility of the individual and the Church's authority does not extend to that of the Bible. Thus the reason doctrines such as the Immaculate Conception of Mary are such a sticking point. Protestants won't buy it because it isn't in scripture. Catholics MUST buy it because it is an official teaching of the Catholic church.

2.Faith alone. Protestants believe that a person is "saved" (meaning his or her sins are covered and that person may dwell eternally with God) by faith alone. No "good works" are necessary. So living a good life and doing more good than evil will not save a person. Only faith in Christ. The Catholic church teaches a slight deviation from this. I don't totally understand it, but I'll do my best. As near as I can tell, the Catholic church teaches that "good works" save a person, but that to do "good works" they must have faith in Christ. Or at least faith in Christ is one way to produce "good works". Like I said, I'm not totally sure.

This latter point was particularly sticky when the Catholic church was selling "indulgences" so that when a person knew he or she was going to sin he could pay for it in advance with good works (giving money to the Church, I think).

While these two points are still irreconcilable between Protestants and Catholics, changes have been made since the Reformation. The Catholic church no longer sells indulgences and their views on Salvation are (I belive) closer in practice to Protestants. Nonetheless, the issue of "works" in Catholisism is still very prevelant, as is the idea of the supreme authority of the Church. Of course, many Protestant churches also seem to adhere to the "supreme authority of the Church" even if not in name.

One thing is that you will find a lot of variation between Protestant churches. My best friend's church (for example) baptises infants. Mine does not, and both are very clear on their stances. However, while points of concern, none of these are deal breakers. My best friend and I have no problem worshiping at each other's churches and being accepted despite the variations in beliefe. All Protestant churches agree on certain major doctrines (this list is not mean to be inclusive)

Salvation by Faith Alone
Authority of Scriputre
The Return of Christ
The Trinity

Hope that (not short) explination helps.