On Ivory
I am not one. I am many.
So imagine your brain is a room. Now imagine yourself in this room. It's probably an empty room. Well that's what I'd imagine it to be since this isn't necessarily my situation. For my situation, imagine there being more than one being in this room who are not you. These other beings are full people like yourself. Pretty neat aye? Now also imagine these other beings (being referred to as headmates) can also control the body. Now you can imagine yourself as being secondary at times. Imagine that some memories are held by only some of these entities and despite you theoretically being around during these times, you don't remember anything.
This is how we experience plurality, or the state of multiple self-aware entities coexisting within a single physical brain. This collective of people? A system, or to us, the Vineyard. While other systems may experience things differently, this is our own experience.