Will-o'-the-wisps are mysterious lights that appear at night, often in marshy or swampy areas. They are typically described as flickering or glowing orbs that can lead travelers off their paths. The phenomenon has been reported in various cultures around the world, often associated with folklore and legends. Scientists believe that will-o'-the-wisps may be caused by the combustion of gases released from decaying organic matter, such as methane. These gases can ignite spontaneously, creating the eerie lights that have puzzled people for centuries. Despite their ghostly appearance, they are a natural occurrence rather than supernatural entities.