Imagine a school of minnows, or a more appropriate species, living down in the deep of the ocean. It's dark, you cannot see, and you only exist as many dozens, just floating amongst each other.
These "minnows" are tiny thoughts merely floating in the back of the mind. These tiny slivers are thoughts and emotions, and vary in sizes. However, once they are exposed to the light, they come together and work as one, as a unit. When a shark comes, only a few will be sacrificed, but the majority of the minnows are protected by the sheer size of the school.
Say the school of minnows finds it's way in a new environment, such as a coral reef, which provides even more protection from sharks and other predators. They are able to eat more, and grow more, and eventually adapt to their new environment, perhaps to the point they are significantly different than their shark-fearing ancestors. Sure, if a shark did find its way to minnow's reef, it would probably have a lovely time, if it weren't for other animals being disturbed (take the octopus, for instance). Either way, the shark goes back to where it came from, and the minnows continue to thrive.
But what makes a minnow different from a thought or emotion is that, if it gets large enough from experience, which may not be much, it has the capacity to make decisions for itself and not just out of habit or survival. When different thoughts and emotions come together, they can form an identity. This identity works like a school of minnows, except it is a singular being. Think of the Pokemon, Wishiwashi, for example. It's school form is really just a thousand or so other Wishiwashi coming in to work together as a singular unit. Each Wishiwashi is a small thought, emotion, and memory that forms into a larger being. It may be possible that two schools can come together and make an even bigger school!
This is the best way I can describe what systemhood is like from my perspective. There was a time where I was many, many parts, who all resonated with the "Samuel" character, be it from The Smiler days or the then-new project "The Monarch Effect." As Maverik, I am the combination of the two, and experienced false memories that I suspect may have been based on the emotions that made me, plus another alter who would become one of our main persecutors. I thought I was a sort of a minion under him, hurting the host for unclear reasons. A pawn would be a better term, as I was still growing and working through who "Maverik" was. I think this alter and I are two halves of the same coin, since we share such a history - perhaps I hated him because I was him, and he is me, but this is for another time. Other fragments I'm related to have since found their own identities, but only after being made to front by the persecutor. Our role, for the most part, is to protect the host in a very specific way (I do not wish to go into detail-it has to do with love), but the approach hasn't always been good or ideal, and is something that we are always working on.
Other alters have different origins, such as Mikeru's original role as a role-playing surrogate or Spencer's being more directly from trauma. I mostly formed into what I am now in order to cope with systemhood and the need for some sort of comfort, and have since grew into myself and had to learn to adapt to whatever changes were happening with my internal projection (like puberty, but your hair changes color and texture every other day, sometimes entire fashion styles - I particularly liked the time I looked like a BATIM character XD).
It was a case where fusion was seen as a good thing, and I am deeply honored to be the first. Many times, it has not worked, as we acted on fear and not understanding what we were and what we were doing. Now that we have a more general idea of what we are and how we work, it isn't as scary anymore. Now, would a therapist that works with systems help? Yes! But, perhaps a DID/OSDD diagnoses isn't the best thing right now.
We turn 20 tomorrow, and that threshold is... something. Sure, we're legally an adult, but I think the idea is that you would have something figured out by now! X) Not to mention all the events leading up to the 4th of July! Goodness! But, once all this has passed, I think things will be a little bit easier. As long as we keep on forward, we'll be okay.
This has been Maverik, and remember.