Electronics is the branch of science that deals with the study of flow and control of electrons (electricity) and the study of their behavior and effects in different mediums such as semiconductors, and with devices using electrons. An example of electronics are radios, computers, and televisions. The study and use of electrical devices that operate by controlling the flow of electrons or other electrically charged particles.
Electronics has been a hobby for as long as electronics has existed. It started with radio in the early 1900s, and has continued to this day. Tinkering. Hacking. Building. Experimenting. Learning.
An electronic hobbyist is someone who enjoys learning more about electronics by building, and designing workable electronic devices.