Electronic music is a genre of music loosely defined as any music made with electronic instruments (such as the synthesizer, turntable, or electronic drums.) Beyond this base requirement, electronic music splits into countless sub-genres, such as EDM, Techno, House, Ambient, Drum 'n' Bass, and Noise, each with their own sub-genres.
It is difficult to pinpoint the exact time electronic music began, although its earliest forms began in the 20th century, with a significant explosion in popularity during the latter half of the century due to the proliferation of synthesizers. This increased popularity gave birth to most of the genres now integral to electronic music.
Although some video game soundtracks of the 8- and 16-bit era emulated the sounds of electronic music, the genre mostly debuted in video game soundtracks following the advent of disc-based storage and the audio improvements that came with it. By far, the most popular electronic genres featured in video games are Drum 'n' Bass, Techno, and Ambient, however genre presence tends to shift heavily with cultural trends, with Dubstep being a common appearance during its heyday in the early-2010s.
Note: Not all chiptune music qualifies as electronic music, nor should the two be confused. Some — but not all — modern chiptune can be considered electronic music, combining qualities from both types of music. However, most chiptune in video games continues to be built around emulating the sound of 8- and 16-bit hardware, rather than for the sake of using electronic instruments.