If I think someone is really going to struggle to understand when I tell them (because tbf it can be confusing!) I tend to tell them that it's like I have all the different Harry Potter houses in my head.
They're all me, they all behave like me, but there are differences in the way I think, speak, behave and present myself.
My alters are very much more fractured than split entirely from me, so it might not resonate with some people at all, but when I explain it this way people tend to understand very quickly.