I of course give myself opportunity to be wrong about this, but I have always believed the seven seals broken from the book in Revelation as being a sort-of overview of the entire tribulation, with each broken seal representing things that will take place over the seven years.
Seal 1: The rider on the white horse with a bow, but no arrows, is given a crown and sent to conquor-this is the rise of the Antichrist.
Seal 2: The rider on the red horse, with a sword, given to take away peace-War begins, or perhaps a great persecution resulting in much death
Seal 3: Rider on the black horse-Famine. Destruction of the food, possibly man-made, maybe the beginnings of which we are seeing with the damage to food by Monsanto and other such groups, artificially controlling the world's food supply.
Seal 4: Rider on the pale, (green?) horse-death, followed by hell-many lost will die violently and by hunger. The sword may represent war, or more likely, governmental power, (Romans 13: 3,4: "For rulers are not a terror to good works, but to the evil. Wilt thou then not be afraid of the power? do that which is good, and thou shalt have praise of the same: For he is the minister of God to thee for good. But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to [execute] wrath upon him that doeth evil.")
Seal 5: The souls of the martyrs slain for the testimony of Christ cry out for vengeance, and are given white robes, told to wait a bit. Those killed, awaiting the deaths of the 144,000 who will be in heaven by Rev 14.
Seal 6: The outpouring of the wrath of God-the stars fall, the great eathquake, from Rev 16:18, the sun black, the moon as blood, the heavens departed as a scroll, mountains and islands moved from their places, and the great and weak men, princes, rulers, and servants crying out that the rocks and mountains should fall on them, hiding them from the wrath of the Lamb. This is clearly the end, as seen in Rev 16, the wrath of God.
Seal 7: Silence, preparation for the judgments of God to begin.
Clearly this is not perfect, but, particularly with the 6th seal, these can't be in order by how they are written, ie, seven seal events happen, then seven, trumpets, then seven vials, because how, then can they be crying out concerning the coming of the Lamb, well before He comes in His wrath, seen in Rev 14-16?
So, I believe this is sort of a prelude, a coming attractions, if you will, the trailer for the tribulation.
But as I said, I am open to being wrong. not perfect, and honestly, I admit that prophecy is not my forte'.