A radio-button, AKA "an option button" is a UI element known to every web/mobile/desktop developer: it allows choosing only one out of a set of options.
Radio buttons are named after the actual buttons used on old radios to switch between radio waves and, sometimes, preset frequencies.
When a button was pressed, all other buttons would pop out, leaving the pressed button the only button in the "pushed down" state. Although in some radios, none of the buttons stayed "pushed in".
The UI concept has later been used in tape recorders, cassette recorders, wearable audio players (the famous "Walkman" and similar), and even VCRs and video cameras all the way up to the early 90s - for the "play/pause/rewind/fast-forward" controls.
The GUI concept was first introduced by researches at Xerox PARC - an R&D company responsible for nearly every cool computer technology we use every day: laser printing, Ethernet, graphical user interface (GUI), object-oriented programming, computer mouse etc. etc.
And the first device that featured a radio-button in its Graphical User Interface was Xerox Star 8010 workstation:
... and was later adopted by Apple Lisa, Apple Macintosh, Atari ST, Commodore Amiga, Visi-On and Microsoft Windows (in this order)
Image credit: Francisco Gonzalez, liz west, Jennifer Woodard Maderazo (cc)