A "Lost Civilization" refers to a society that has disappeared or declined significantly, leaving behind remnants of its culture, architecture, and artifacts. Examples include the Maya, Inca, and Ancient Egypt, which once thrived but eventually faced collapse due to various factors such as environmental changes, warfare, or disease. Archaeologists study these remnants to understand how these civilizations lived, governed, and interacted with their environment. Discoveries like the Machu Picchu in Peru or the Minoan ruins on the island of Crete provide insights into their advanced technologies, social structures, and daily life, helping to piece together the history of humanity.