When there is an applied voltage or an electric field across a semiconductor, the charge carriers, which is either electrons or holes, move and produce a current. Negatively charged electrons move towards the positive side of the applied voltage while positively charged holes move towards the negative side. This movement or flow of the charge carriers due to applied voltage is called drift. Hopefully this doesn’t confuse you as it did me - when I think “drift”, I think something that is semi-randomly bobbing around in the ocean and this threw me off for quite awhile. In this case, “drift” is purposeful and follows the direction of the applied voltage or electric field. It’s the movement you’re actively controlling when you change the voltage across the device.
Electrical resistivity and its reciprocal, conductivity, characterize current flow in a material flow when an electric field is applied. Charged particles move or drift in response to the electric field.
Microelectronic Circuit Design, 4th Edition by Richard C. Jaeger & Travis N. Blalock