4-beat (also known as hardcore or happy hardcore) is a breakbeat style of music that emerged around 1993. It evolved from breakbeat hardcore emanating from the United Kingdom rave scene. Due to the sheer scale of the United Kingdom rave scene, the popularity of this particular music was largely limited to England where it was almost exclusively produced and played.
Breakbeat hardcore was originally referred to as hardcore by ravers in England. As such, this evolved style was also alternatively known as hardcore or happy hardcore — the latter meaning a happier variant of this breakbeat styled hardcore, thus happy hardcore (i.e. happy breakbeat). Darkcore was the short lived counter-movement to happy that occurred at the same time.
The name happy hardcore should not be confused with other things that are also referred to as happy hardcore, as that term is much shared across the world to describe different sounding things that have their own development.
Also in this article, 4-beat is not a musical term commonly used to describe a drum beat time signature found in most types of modern music, but is rather a specific name used to describe a breakbeat music style.
Read more about 4-beat: Characteristics, Terminology