Difference between thermistor and temperature sensor?

A thermistor is a temperature measuring device which acts like a temperature sensitive resistor. It is an active device that requires a current flow to measure its resistance so that the temperature may be calculated and/or displayed.

A thermocouple is a device composed of two dissimilar metals fused together. An electrical potential occurs across the junction of the metals. As the potential is influenced by the temperature of the metal junction the output voltage can be measured and calibrated to show the temperature at the joint.

Both devices may be employed to measure the temperature within a fixed space, or on a probe to measure the temperature at a remote point or points.