Software frameworks for building video games that handle rendering, physics and sound, such as Unity and Unreal. Artists use them to make real-time worlds and simulations.
The "digital performance" is just another name for "machinima," which are performances acted out in video game engines.
Brennan Wojtyla, Mika Ben Amar & Brennan Wojtyla on Life Online
My collaborator Darren Zhu, a synthetic biologist and creative technologist, sent me a paper a couple of years ago by Stanford researcher Muyuan Chen about rendering full protein structures inside Unreal Engine. That was a major moment in my intellectual life.
Wendi Yan, Wendi Yan & Karyn Nakamura on the Artifice of Knowledge