Or…
the 4-8 second phonological loop in the brain which loops and loops around, verbally expressed inner chatter which is fed by memories and spoken in your own voice, but whose sources are likely words previously read, heard, spoken, seen, combined with original connections from the base materials influenced by one’s temperment at the time.
A Myth of the modern era: “Voices in the Head = Crazy”.
Reality: “Voices in the Head = Normal”
It only becomes a problem when you get buried under them.
It’s called “Thinking”.