Tell me what it means

Yes, and I was astounded to learn that it's function is actually the opposite. It slows your computer's processor down to near-8086 speeds for software (games, mostly) that didn't use timers but was rather tied directly to the CPU clock speed.

Unless you mean the "turbo" button on your NES Advantage controller. That button's primary function was to annoy the shit out any adults within earshot by spamming the jump noise or pause-unpause jingle.