”Electronic music” generally implies the use of electronic instrumentation to create (synthesize) or to manipulate sound.
In the mid-20th century, the term “electronic” might have meant more; as then music was always acoustic, being performed by live players who bowed or plucked or struck objects in order to make air vibrate. Around 1942 French radio broadcaster Pierre Schaeffer created what is known as the first electronic music studio; using a variety of microphones, phonographs, variable speed tape recorders and records of natural sounds he began creating pieces based on processing pre-recorded sounds (“musique concrete”).
Since then, electronics have become an integral part of most modern music. So today the term “electronic music” only suggests that the quality or character of the music sounds synthetic, processed/manipulated by electronics, as opposed to being performed by acoustic instrumentation.