It's a resistor that changes values based on the temperature.
(1) Their are therocouples of J and K type, and others J-K most often used. (2) RTDs 2,3,4 wire types. (3) Thermisters
Thermistors can be used for temperature sensing and control in devices such as thermostats, air conditioning systems, and refrigerators. They can also be used in medical applications for monitoring body temperature or in automotive applications for measuring engine temperature.