 Potentiometer taper describes how a pot's resistance changes over time while the shaft is continuously rotated. It's determined by varying the amount of resistive material deposited across the pot's internal track. The two most common taper types are linear, where the pot's position has a linear relation to its resistance, graphing as a straight line over time, and audio, aka log taper, where resistance increases with a logarithmic curve, which correlates with how humans perceive changing sound levels. In actuality, many audio pots will use a linear approximation of this curve, but the effect is nearly identical. Most often you'll find audio taper pots labeled with a letter A prefix or suffix, which makes sense. While linear pots usually use the letter B, they are pretty basic.