Electrochemistry is a branch within the field of chemistry which involves the intersection between chemical reactions and electrical currents. Some chemical reactions can be catalyzed by the presence of an electrical current, and conversely, it is possible to generate electricity through the process of a chemical reaction. While this pursuit may sound esoteric, chances are very high that you are benefiting from electrochemistry at this very moment, or that you will be at some point today, because it is the underlying process behind a wide range of things, from chemical signaling in your own body to the operation of a car battery.
Modern electrochemistry has diverged significantly from the 18th century roots of this field of study. In addition to inspiring a great deal of pure research, electrochemistry is used in a wide range of industrial processes, and in technology utilized in numerous settings. Earlier researchers were primarily interested in explaining phenomena they didn't understand, while modern researchers are interested in finding new applications for electrochemistry, and in understanding complex electrochemical reactions. They are also interested in understanding electrochemical reactions on a very small scale and basic level, now that the technology for precise observations of this type is available.
All living organisms use electrochemistry to one degree or another, from the electric eel to the humble houseplant. Living organisms have noticeable electric fields which are generated by chemical reactions in their bodies, and electrochemical reactions are involved in a number of biological processes. For this reason, some biologists are interested in electrochemistry, as are other people who work in the natural world or are interested in the natural environment.
One of the underlying concepts in electrochemistry is the reduction/oxidation or redox reaction, which describes a situation in which electrons are gained or lost. While a small scale reaction will not generate usable energy, it involves the very same electrons which move through the wiring in a home, and these reactions can be used to generate a usable electrical current. Processes like photosynthesis and respiration involve redox reactions, making them electrochemical in nature.
Electrochemistry is also used in scientific laboratories, for processing and analyzing a range of materials. It is also used in processes such as electroplating, in which the property of electrodeposition is harnessed, and in the operation of batteries, which utilize a chemical reaction to generate electrical energy. Another example of a natural electrochemical reaction is corrosion, especially iron oxidation, which is better known as "rust" among lay people.