basically he was tracing his program and noticed that it was trying to execute code outside the expected area
apparently something to do with an interrupt (breakpoint?) messing with the program counter (stores the address of the next thing to execute)

but thats besides the point
he was just using an experience to portray the age old observation that saying things aloud and/or trying to explain things aloud often helps to bring clarity in thought

anyways i dont usually hold conversations with myself aloud for the sole reason that im lazy and would rather hold a conversation in my head than bother my jaw muscles and my vocal chords
the same goes for thinking things aloud.. for most things i can usually just focus on single question/statements at a time.. and "talk" in my head
for something a little bit challenging i might start mumbling/noises or saying random words just to distract myself
last resort would be to start talking