This is the seventh and final bowl judgment, and the last of the 21 judgments of the book of Revelation.  At this point all of them are complete and Jesus now begins preparations to ride in and officially reclaim Earth for Himself.  But before then comes an interesting series of events, sorta like a victory celebration, begins in Heaven, proclaimed with a shout of "It is Done!" which is quickly followed by lightning, rumblings, peals of thunder and a severe earthquake.  Basically this constitutes a statement of "I've won and here's the proof."  This proof consists of a massive thunderstorm of quite literally biblical proportions, and an earthquake that is literally the greatest ever seen, even exceeding the great earthquake of Rev 6:12-17.

In fact, the Earthquake is so powerful that it is described in Revelation as being "like no other earthquake since mankind has been on earth, so tremendous was the quake."  It even speaks of how the quake divides Jerusalem into three parts, and somehow judges the capital city of the AntiChrist, otherwise known as Babylon.  Which Babylon that is, it's not clear.  Some believe the city of Babylon that's in Iraq, but at the present time it doesn't look like that's the one.  So therefore it must be a different city so named because of what it is used for and the activities in its walls, but which carries a different name in real life.

Another side effect of this earthquake is that it destroys every single mountain and island on the planet.  Another side effect is a plague of hailstones weighing about 100lbs each.  (see the 100lb hailstone prophecy for more details on this.)  If one were to view this in military terms, this would be God delivering His opening artillery bombardment and softening of the enemy before beginning the main attack.  And, as expected, all those who are unsaved continue to curse God and shake their fists at Him because of the severity of the plague.  Well, assuming they survived.

Side note: If you want to learn more about the fall of Babylon and its final destruction, the next three chapters, 17-19 cover this in detail, both who the city is, and how it's destroyed.  It's worth the read.  However, understand that this is different than the "Burden Against Babylon" which only covers the destruction of Iraq and the ancient city of Babylon, hence the belief that the final city as spoken of in Revelation is a different one than the literally named one.