What are fertilizers and pesticides?

Fertilizers are materials designed to feed (provide) nutrients to plants. They come in liquid and dry forms, fast and slow release, inorganic and organic, and so on. Pesticides are materials designed to eliminate, prevent or control pests, such as: insects, slugs, snails, diseases like fungus (mildew, rots, smuts), and so forth. Herbicides are materials designed to eliminate, prevent or control unwanted plants (what we normally call "weeds").