There are 6 seals that lead up to a period of great turmoil, the opening of the seventh seal unleashes that great turmoil.
A Period of Turmoil
This is described as a sequence of seven events, each heralded by the “sounding” of a Trumpet, the last of which begins another sequence of seven events — of vials (bowls) of judgement. The entire period may last 7 years (some say 10 or 20 years), but what is certain is that the last 3.5 years of this period—known as the Great Tribulation (or sometimes just “Tribulation”)—will be a time of great anguish and sorrow.
The first four trumpets are encapsulated, each one in turn, by the four horseman of the apocalypse, which bring us up to that Great Tribulation, described by Messiah Yeshua:
The fifth trumpet (also described as the first “woe”) involves the Destroyer (Abaddon) and his army.
The sixth trumpet (the second “woe”) releases the four [demonic] angels bound at the Euphrates River, to kill a third of mankind with an army of 200 million.
There are then “7 thunders” that scripture avoids to detail before the 7th and final Trumpet (and third “woe”) is sounded. This marks the start of the 7 bowls of God’s wrath.