Ninjas were covert agents in feudal Japan, known for their skills in espionage, sabotage, and guerrilla warfare. They often operated in secrecy, gathering intelligence and carrying out missions for samurai or feudal lords. Unlike the samurai, who followed a strict code of honor, ninjas used stealth and cunning to achieve their objectives. The term "ninja" is derived from the Japanese characters for "to endure" and "to hide." They were trained in various martial arts and tactics, using tools like shurikens and smoke bombs. Today, ninjas are popular figures in popular culture, often depicted in movies, video games, and comic books.