Great Distress and Deceivers

Matthew 24:21-28
21 For then there will be great distress, unequaled from the beginning of the world until now-and never to be equaled again. 22 If those days had not been cut short, no one would survive, but for the sake of the elect those days will be shortened. 23 At that time if anyone says to you, 'Look, here is the Christ!' or, 'There he is!' do not believe it. 24 For false Christs and false prophets will appear and perform great signs and miracles to deceive even the elect-if that were possible. 25 See, I have told you ahead of time.

26 "So if anyone tells you, 'There he is, out in the desert,' do not go out; or, 'Here he is, in the inner rooms,' do not believe it. 27 For as lightning that comes from the east is visible even in the west, so will be the coming of the Son of Man. 28 Wherever there is a carcass, there the vultures will gather.
(from New International Version)

Great distress, widespread trouble or tribulation such as has never been seen before. That's a lot of trouble. The book of Revelation goes into detail about the tribulation that is being referenced here. Disasters such that 1/3 of the earths population is killed. Now this time is limited to seven years. It begins when the Anti-Christ signs a 7 year covenant,or peace treaty, with Israel.

During this time there will be false prohpets that are empowered by Satan to do miracles for the purpose of deceiving people. They will convince people that the Anti-Christ is the messiah and massive groups of people will follow him. Verse 27 gives a warning and a description about how Jesus will return so that we will know for sure and not be deceived.