Final answer:
A "happening" is a type of Performance Art, initiated by Alan Kaprow in the 1950s and 60s, that often engaged the audience in the art, contributing to the development of Conceptual Art.
Step-by-step explanation:
A "happening" is a type of Performance Art, which was a movement initiated in part by Alan Kaprow during the 1950s and 60s. Happenings involved a sometimes invited, sometimes ad hoc audience who would interact with the activities presented, often blurring the lines between the performer and the audience. Although Happenings could be similar to a kind of street theater, not all took place outdoors and they were key in the development of Conceptual Art, which emphasized ideas over physical art objects.
Performance art generally involves the body of the artist and may incorporate audience participation, be scripted or unscripted, and random or carefully organized. Performance art challenged traditional art forms by creating live events which often transformed ordinary human activities or concepts into an artistic spectacles, as seen with Fluxus artists like Yoko Ono. Furthermore, performance art and Happenings played an important role in democratizing art by taking it out of the elitist confines of galleries and museums and insisting on work that engaged with the contemporary world.