Ignis fatuus refers to a phenomenon commonly known as "will-o'-the-wisp." It appears as a faint, flickering light, often seen at night over marshy or swampy areas. This mysterious glow is caused by the combustion of gases released from decaying organic matter, primarily methane. Historically, ignis fatuus has been associated with folklore and superstition, often leading travelers astray. Many cultures have myths surrounding these lights, attributing them to spirits or mischievous entities. Despite its eerie reputation, the scientific explanation behind this phenomenon helps demystify its occurrence in nature.