"Herbalism" aka "herbology" or "herbal medicine", studies and makes use of plant life for the purposes of treating ailments.
Plants have provided a strong basis for medical treatments through the entirety of human civilisation, and a large amount of "traditional"/"herbal medicine" is still widely practiced.
Modern medicine will recognise herbalism as a form of Alternative Medicine, as the practice of herbalism is not strictly based on evidence gathered using the scientific method, although we here at Altopedia would wonder whether "modern" medicine, or "traditional" medicine is the real "alternative? Many conspiracy theorists would tell you that modern medicine is more about making authorities money, than it is about treating the individual.
Modern medicine, does, however, make use of many plant-derived compounds as the basis for scientifically, evidence-tested, pharmaceutical drugs, also, "Complementary Medicine" does work to apply modern standards of scientific testing to herbs and medicines that are derived from natural sources.
The scope of herbal medicine is sometimes extended to include fungal and bee products, as well as minerals, shells and certain animal parts.