>>507798391Correct me if I'm wrong, but I believe the original Vanilla server infrastructure could only hold about 3-10,000 players per "realm". With the advent of better hardware and less limitations put on it by the old backend software, Blizzard have added "layers" instead which hold about the same number of players.
When one layer is full, another is added to hold more people.
This is done to allow players to stay together without having to add or remove realms as the population changes.
When someone invites you to their group, you are pulled into "their" layer.
