Is pesticide used for killing insects?

Pesticides is the general term that's used to describe the chemicals that are designed to kill pests. The first part of the Word, which is 'pest-' in this case, identifies the intended target or victim of the chemical. The second part of the Word, '-icide', explains the intended, terminal action to whatever the pest is.

There also are specific chemicals that kill specific pests. For example, 'fungicides' kill fungi. Chemicals identified as 'insecticides' kill insects. Those identified as 'miticides' kill mites. 'Herbicides' kill plants, usually weeds, 'rodenticides' kill rodents, etc.