What does atonal mean in music?

In music, atonal refers to music that does not have a tonal centre, or key, and lacks the traditional harmonic structure and resolution found in tonal music. Atonal music uses dissonant intervals, such as augmented seconds, tritones and unresolved sevenths, to create a sense of tension and ambiguity. Atonality emerged as a reaction against the strict rules and conventions of traditional Western music and allowed composers to explore new possibilities and express a wider range of emotions. Some notable composers who used atonal techniques include Arnold Schoenberg, Alban Berg, and Anton Webern.