Minecraft:Generations is a chainworld versions of Minecraft. This means it's played with no regeneration, survival, and only 1 life. You name someone to take your place when you join, and once you are dead, that's it and they take over.
This version is for non-Java players and involves 2 players at the same time: An Elder (been there a while) and a Prodigy (new to the realm). Elder has access to a few extra things that their predecessors have put aside.