Guerrilla marketing is an unconventional marketing tactic that uses surprise and creativity to promote products and services. It aims to generate buzz and engagement rather than rely primarily on large advertising budgets. Some key types of guerrilla marketing include viral marketing, which spreads through social networks, street marketing which engages directly with the public, and grassroots marketing which leverages personal relationships. Guerrilla marketing has historically relied more on engagement than education and has grown in popularity since the 1970s as mass advertising became less effective.