They’re not physical locations that system members actually live & walk around in, but the brain may make them perceive it that way.
When we front, we can “remember” what happened in our innerworld while we were there. Since we share a brain, we all have the same “storyline” there, which has created consistent “memories” from within our innerworld over the years.
We’ve had things happen there that have helped us process & recover from things that happened in the outerworld. (It’s why it’s used as a therapeutic technique.)
There’s a fine line with it. It’s possible to rely too heavily on the innerworld to escape the stress of this life, which, for many CDD systems, was the only way they could survive. Once it’s safe to do so, it is important to draw up a healthy distinction between innerworld reality and physical reality. But, on the other hand, entirely denying the legitimacy of innerworld events can greatly hinder healing.
Oftentimes, innerworld happenings are metaphorical. They occur because there’s something the brain/system needs to work through. For example, a “physical fight” occurring within the innerworld may represent clashing morals between two system members, and signify that the misalignment needs to be addressed.
So, are innerworlds “real”? Maybe not in the way the walls of my house are, but it’s real in that it’s a significant part of how my brain functions. To deny that reality entirely is to deny the very thoughts in my head, simply because I can’t touch them & other’s can’t see them.