Basically a Potentiometer is the same a rheostat or a varibale resistor. Thats how many dimmers work, such as your guage cluster lights in your car.
The variable resistor get an input voltage of say 5v. Depending on where the wheel is in realtion to the contacts inside, the output voltage can be no higher than 4.97v and the lowest is somewhere at .1 or .01v
Obviously the more resistance put onto the incoming voltage the less the output voltage would be.
This means that the rheostat output on the chip at 4.97 volts would prolly block out everything on the LCD while at .01v output the LCD should not show any text.
that took about the same time it would have taken to search up a dead thread or tell the guy to search.