Resistance: 100 kOhms
Power Rating: 18 mW
Tolerance: 1 %
Termination Style: Radial
Operating Temperature Range: - 55 C to + 200 C
Dimensions: 0.8 mm Dia. x 0.8 mm W x 1.4 mm H
Lead Diameter: 0.15 mm
The thermistor senses the temperature of the Hot End. Often a second thermistor senses the temperature of the Heated Bed.
Thermistors are resistors that change of resistance with a change in temperature.
Good qualities of thermistors are a predictable, accurately known resistance value at every temperature in its operating range.
The lowering, or rise, depends on the type of thermistor per degree Kelvin (or Celcius, if you prefer), this is called its coefficient.
Positive thermal coefficient (PTC) will increase in resistance with an increase in temperature, negative ones (NTC) will decrease. But the formula in practice is not linear, so sometimes an accurate table of measurements is better than the linear formula. These measurements can usually be found in the datasheet that accompanies the thermistor.