Live Streaming & Premieres
Co-streaming
Also called: co-stream, Go Live Together, collab stream
Two different things share the name. The first is a guest stream, where another creator joins your broadcast and both audiences land in one chat, which YouTube supports on mobile through its guest streaming feature. The second is event co-streaming, common in esports, where the organiser grants permission for other channels to carry the official feed and react to it.
Permission is the part people skip. Restreaming a match, a keynote or a fight without a licence is a copyright claim waiting to happen, and the fact that other channels are doing it is no defence.