There can be a lot of traffic in World of Warcraft Classic that makes some of the game feel like it’s running through mud, and it can become difficult to play if there are too many characters at the same location. To make this process easier, Blizzard created a feature called layering that places characters that are in the same area in different instances, basically.
Players in the same layer can see other players also in that layer, but they can’t see anyone, not in that layer. If you’re trying to group with the same players, you want to make sure you play on the same layer. It’s similar to sharding. Blizzard did detail they only planned to introduce layering for the first few weeks of World of Warcraft Classic.
All you have to do to change the layer of your World of Warcraft Classic game is to group with someone in a different layer. This can be someone you’re attempting to meet up with or someone from a guild. Group up with them, and if you’re in separate layers, you’ll be transported to the group leader’s layering, bringing you both to the same instance.
If you want to take advantage of layering to farm mobs for a quest, you can kill them in your layer and then have a friend from another layer invite you to their group. You’ll be transported to that location, and a fresh series of mobs will appear once more. It’s a good way to ensure certain players are not camping a certain mob and gives you multiple chances at a particular series of NPCs.