There are letters, seals, trumpets, woes, and plagues. I will fit them together in a way that makes it less confusing.
First came the seven letters to the churches, or ages of the churches. All the others are lists of events that happen sequentially, so it stands to reason that the letters are the same. They start from the very first churches set up by the apostles and cover up to the end of the age. Next come the seven seals, which cover the age of Laodicea, the last age. Revelations were written for this age and take over from Daniel. Although, Daniel still has events from the end of the age in it. Then the seven trumpets. At the start of the seven trumpets in Rev 8:5, it says, “Then the angel took the censer and filled it with fire from the altar and threw it on the earth, and there were peals of thunder, rumblings, flashes of lightning, and an earthquake.” Of the seven trumpets, the last three are regarded as woes as well in many commentaries, but that is not entirely correct. The woes have a spiritual component beyond the calamities. The first six trumpets are aimed at the earth and are corporeal disasters. The opening of the bottomless pit is the first Woe. The second has two witnesses, and the third is not mentioned. We know what it is by deduction only. The woes are a bit strange and will get covered in their section. The plagues run at the same time as the trumpets. While the trumpets are events, the plagues are the wrath of God on the wickedness of the human spirit. Some are different aspects of the same event. You could call 8/9 the calamities and 15/16 the tribulations.