The third horseman is described in
Revelation 6:5-6, “...and there before me was a black horse! Its rider was holding a pair of scales in his hand. Then I heard what sounded like a voice among the four living creatures, saying, ‘A quart of wheat for a day's wages, and three quarts of barley for a day's wages, and do not damage the oil and the wine!’” The third horseman of the apocalypse refers to a great famine that will take place, as a result of the wars from the second horseman. Food will be scarce, but wine and oil will still be readily available.
The fourth horseman is mentioned in
Revelation 6:8, "I looked, and there before me was a pale horse! Its rider was named Death, and Hades was following close behind him. They were given power over a fourth of the earth to kill by sword, famine and plague, and by the wild beasts of the earth." The fourth horseman of the apocalypse is symbolic of death and devastation. The fourth horseman of the apocalypse will bring further warfare and devastating famines along with awful plagues and diseases.
The last two horsemen of the apocalypse are precursors of the terrible judgments that come later in the final three and a half years of the seven year Tribulation, known as the Great Tribulation [Revelation chapters 8-9 and 16].