These are chemicals used to destroy unwanted plants called weeds that can be either terrestrial or aquatic. There are two kinds of herbicides.
Species-specific (selective) herbicides are designed to kill a specific kind of plant only, leaving other desirable plants unharmed.
Non-specific herbicides kill every plant they contact. They work in two ways, either by contact or systematic action where the herbicide is absorbed into the plant either by its roots or its surface, and then moves throughout the entire plant shutting down all of its functions. They come in granule or liquid form to be mixed with water.