Airplay 2 enhances AirPlay by allowing media content to be streamed to multiple AirPlay 2 devices at any one time. A facility previously only available if using iTunes from a Windows or Mac computer.
It’s latest device, the Apple HomePod is due to be AirPlay 2 enabled in 2018.
Airplay 2 became available in early releases beta releases of iOS 11.3. It has since been removed while we await any further developments.