Insecticide is a chemical or biological substance used to kill, repel, or control insects that harm crops, spread diseases, or cause damage to property. These substances target pests such as mosquitoes, termites, beetles, and caterpillars by affecting their nervous system, growth, or reproduction. Insecticides come in various forms, including sprays, powders, baits, and granules, and can be synthetic or derived from natural sources like plants. They are widely used in agriculture, public health, and household pest control. Proper usage and safety measures are essential to prevent harm to humans, animals, and the environment while ensuring effective pest management.