Insect pheromones are a vital medium for communication and play an important role in behavior, social interactions, mating and development. There are numerous insect pheromones which transmit all kinds of information accurately, thereby enhancing the survival and reproduction of individual insects and colonies. However, how can millions of insect species produce such a diversity of pheromones? How can they communicate accurately and avoid interference from the pheromones of other species? This paper reviews the diversity of pheromone chemical structures, pheromone combinations, their biological functions and biosynthesis pathways. The diversity of odor-related proteins and the mechanism of pheromone recognition are also discussed.