Planets are in motion around the Sun. Sometimes the planets’ positions are aligned that they appear close to each other in the sky, and less frequently, involving more than two planets.
One such alignment of planets occurred in May 2011 where Mercury, Venus, Mars, and Jupiter are all appeared close together. Mercury and Venus are closer to the Sun than Earth, while Mars and Jupiter are farther. Flat-Earthers cannot understand how all of these planets can appear close to each other in the sky, and they use it to discredit science. In reality, this diagram can easily explain the general positions of the planets during the phenomenon.