A UFO, or Unidentified Flying Object, refers to any aerial phenomenon that cannot be immediately identified. This term is often associated with sightings of strange objects in the sky, which may include anything from weather balloons to experimental aircraft. The key aspect of a UFO is that it remains unidentified at the time of observation. While many people associate UFOs with extraterrestrial life, most sightings can eventually be explained through natural or man-made causes. Governments and organizations, such as the U.S. Department of Defense, have investigated UFO reports to determine their origins and ensure national security.