Recall the concept of a voltage divider. You can replace a fixed-value resistor with an analog sensor like a thermistor or Hall sensor. Changing the value of the fixed resistor is a way to tune the output to a particular range.
A potentiometer is a voltage divider with a movable contact. It can be used to provide a variable voltage, or act as a variable resistance.
Map function
Analog Read Resolution
How fast is a conversion?