Short answers, pulled from the story.
The core members included Christopher Marlowe, Robert Greene, Thomas Nashe, John Lyly, Thomas Lodge, and George Peele. These six men formed the association while studying at Cambridge or Oxford universities.
George Saintsbury coined the phrase in his 1887 book History of Elizabethan Literature. No one used this label while these playwrights were alive during the late 1500s.
University graduates faced a stark reality where their education offered no clear path forward into traditional careers. They could not take up humble trades without feeling loss so employment in theater became all they had available.
Edward Albert stated that the plays shared heroic and usually tragic themes within a specific heroic style. G. K. Hunter argued that new Humanistic education allowed these writers to create complex commercial drama.
A pamphlet titled Greene's Groats-Worth of Wit appeared after the death of Robert Greene containing an apparent attack on Shakespeare as an upstart crow. Scholars believe this text was actually written by Henry Chettle rather than Greene himself.