Just a note to anyone else who may post, be on your best behavior in this. We haven't done too bad in the UK election thread, so let's keep up the good work in this one, too. We don't want to ban topics on politics, and certainly don't want to have to re-close GC, so we just need to keep these threads respectful. Thanks, Bignose
"Democrat" and "Republicans" are just he names of the two main political parties in the US. The Democratic party tend to be more liberal, and the Republican party tends to be more conservative. There hasn't been a significant third party in quite a long time in the US. The word choice "tends to be" is important, because any individual member of the party may have different beliefs on specific issues, and sometimes even the entire party can take a different view on some issues.
"Liberals" (also known as leftist) tend to be more about attempting to equalize people today, especially the disadvantaged. That is, they tend to be larger proponents of "social justice" reforms, and social welfare. Projects like welfare, unemployment, and subsidized health care, for example. Because of their leaning toward projects like that, they tend to necessarily be in favor of higher taxes (to have the money to fund those projects, and to help "level" the field between what they see as the advantaged rich and the disadvantaged poor) and big government, which has to run these programs.
"Conservatives" (also known as rightist) tend to be more about attempting to give all people an equal chance to start, but then firmly believe that what each person makes of themselves is earned and therefore should be kept. They would be more in favor of subsidizing schools so that every person has that same chance at an equal education. However, they would be against higher taxes, and against social welfare programs -- because if each person is given the same initial point, what happened since then is on them. Conservatives also tend to be larger supporters of businesses, and in capitalism in general -- they believe that large businesses means more jobs for more people and everybody is better off.
Social democrats are just people with liberal leanings that embrace the tenants of socialism more closely. You can look up what a socialist government is versus a capitalistic government -- they share little common ground. Christian democrats are democrats that follow the Christian religion.
I would strongly suggest you find a good textbook on politics or political science; it will discuss these concepts in much greater detail. The few paragraphs above really don't due either side any justice at all, as almost every single topic is more complicated than just a few lines.