Guerrilla marketing is an unconventional advertising strategy that utilizes low-cost tactics like pop-up ads, stickers, and ambush marketing to promote products in a localized or surprise way. The term was coined in 1984 to describe smaller marketing groups using surprise and sabotage against larger competitors. In the 1960s, firms adopted guerrilla tactics like ambient, presence, experimental, and street marketing to creatively outdo rivals with fewer resources. While cost-effective and eye-catching, guerrilla marketing requires time and risks negative perceptions if not carefully executed within the law.