Chemical pesticides are considered as the most effective and reliable agents to control and to kill the pests from agriculture, residential as well as from the public places. Pests such as algae, bacteria in plants/soil, birds, fungi, insects, mammals (mice, rats and moles), mites and ticks, nematodes, slugs, snails and weeds are effectively controlled by the use of pesticides. Also, they are beneficial to decrease the burden of deadly diseases (malaria) spread or caused by the vectors. Though the pesticides are beneficial for enhance production and yield of agriculture sector, increased food productivity and public health, they have adversely impacted the environment and human health. This review focuses on pesticides with respect to definition and toxicological classification using various criteria. This study recommends practice of Integrated Pest Management (IPM), strict use of pesticides that are labelled for the intended crop and pest, consideration of application site characteristics and location of wells, ponds and other water bodies, measuring accurately the quantity and specified dilutions, maintaining application equipment and calibrating accurately, mixing and loading carefully, preventing back siphoning and spills, considering the impact of weather and irrigation, safe and secure storage and disposal, leaving buffer zones around sensitive areas and to reducing off-target drift.