basically, different parties like Labour and Tories. The system is different and the parties are different too, but Democrats would be closer to Labour and Republicans closer to Tories
Not being overly familiar with political systems and divisions in the U.K., it is safe to say that Democrats lean to the liberal and Republicans are conservative. Democrats believe in Big Government, and Republicans are more self reliant and want smaller government and hence, fewer and smaller taxes... greatly ovsr-simplified, of course. Both parties have their extreme elements...