And where can I find more information about the book of Revelations and the Horsemen's association with it in general? I really just need a summary, but I didn't want to ask for that in fear of breaking any rules.
I'm wondering what the first interpretation was, and what the Horsemen's purposes were.
The 'original' description is the one in the book of Revelation (no s necessary):
6 Then I saw the Lamb open one of the seven seals, and I heard one of the four living creatures call out, as with a voice of thunder, “Come!” 2 I looked, and there was a white horse! Its rider had a bow; a crown was given to him, and he came out conquering and to conquer. 3 When he opened the second seal, I heard the second living creature call out, “Come!” 4 And out came another horse, bright red; its rider was permitted to take peace from the earth, so that people would slaughter one another; and he was given a great sword. 5 When he opened the third seal, I heard the third living creature call out, “Come!” I looked, and there was a black horse! Its rider held a pair of scales in his hand, 6 and I heard what seemed to be a voice in the midst of the four living creatures saying, “A quart of wheat for a day’s pay, and three quarts of barley for a day’s pay, but do not damage the olive oil and the wine!” 7 When he opened the fourth seal, I heard the voice of the fourth living creature call out, “Come!” 8 I looked and there was a pale green horse! Its rider’s name was Death, and Hades followed with him; they were given authority over a fourth of the earth, to kill with sword, famine, and pestilence, and by the wild animals of the earth.
The author is almost certainly drawing upon Old Testament imagery, specifically Zechariah 6:1-8, and 1:8-15, which you can look up on your own time. I'm not really sure what kind of information you are after though. Perhaps you are looking for some kind of history of interpretation? The more specific your question, the more specific my answer can be.