The easiest part of understanding what is is that botanist do is this: they study plants! But there is so much more. There are 17 sub fields or specialties that will be briefly described in this article. Each one can involve a lifetime of study and work.
Botanists work in a vast array of job opportunities and specialties! Some are involved in studying the most promising plants for drugs, food, ant nutrition . There are some who examine properties of plants for use in the textile field. Forensic scientists are very interested in botany, since plant material, seeds and other components can tell about a where person has been, alive or in death, and if a plant component was a cause of death. As more humans depend on more food, botanists study ways to make crops more productive, nutritious and resilient. Even the relationships between plants and the environment, the atmosphere and societies are studied.
Most botanists work in colleges and universities, with the next largest group in a long list of government agencies. Industry is third most likely for botanists.
There are major sub fields of botany that have been established for a while. But the sub fields and specialties of botany are evolving and growing, with some disagreement or differing ideas as the newer specialties work their way toward becoming well defined and established fields of study.
Genetics, systematics, cytology, anatomy, morphology, plant physiology, pathology, and ecology are the established broad sub fields of botany.
The newer specialties are:
Economic botany (the relationships between people and plants, how people use plants with a little anthropology thrown in)
Phytosociology (the study of plant -not people- communities and the relationships between species of plants)
Ethnobotany (how indigenous populations make use of plants)
Biometerology (a newish subfield that relates plants with environment)
Plant ecology (ecology of vascular plants on land and in wetland ecosystems)
The more established sub fields are:
Plant pathology (diseases and the changes that they cause in structure and function)
Horticulture (the science of cultivating plants)
Agronomy (soil management and study as it relates to crop management)
Plant taxonomy (categorizing plant species, these days using DNA analysis)
Paleoclimatology (how plants have contributed to the atmosphere through all of history!)
Palynology (study of where a body has been laying in a particular spot, and forensic botany)
Bryology (mosses and liverworts)
Dendrology (woody plants)
Palynology (spores and pollen, both fossilized and current)
Xylology (study of the structure of wood)