I remember the days of cpu clock speed being displayed on the outside of the computer case using an led display. There was also this turbo button but I'm not sure whether that really did anything.
Generally, Turbo toggled some form of slow mode. Back in the XT era, enough software relied on the original 4.77MHz CPU clock of the PC and XT that faster Turbo XT clones running at 8MHz would have a switch to slow things back down. It persisted for a while into the early ‘90s as a way to deal with software that expects a slower CPU, although later implementations may not slow things down all the way to an XT’s speed.
