The term pesticide includes many kinds of ingredients used in products, such as insecticides, fungicides, rodenticides, insect repellants, weed killers, antimicrobials, and swimming pool chemicals, which are designed to prevent, destroy, repel, or reduce pests of any sort.
Basically, pesticides are substances intended to be used for destroying, preventing, mitigating or repelling any pest.
Pesticides save farmers money by preventing crop losses to insects and other pests, farmers get an estimated four-fold return on money they spend on pesticides.