How do pheromones work?

A pheromone (from Greek φέρω phero "to bear" + hormone from Greek ὁρμή - "impetus") is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual.[1] There are alarm pheromones, food trail pheromones, pheromones, and many others that affect behavior or physiology. Their use among insects has been particularly well doented. In addition, some vertebrates and plants communicate by using pheromones.