PTC thermistor vs. NTC thermistor for measuring the temperature of a liquid
Most thermistors used for measuring temperature are NTC. They are specified relatively tightly in terms of their parameters for that application.
They usually change quite a bit with temperature, of the order of -5% for every degree C, so that they end up being very nonlinear, to the point that for a wide temperature range you need a lot of dynamic range in the measuring circuitry or you lose resolution at the extremes. For example a thermistor may be 10K nominal at 25°C but only 516 ohms at 125°C, and 210K at -40°C.
There are some PTC thermistors designed for measuring temperature, they tend to have more gentle temperature coefficients (such as the silicon resistance types).
There are also RTDs which are (sometimes pure noble) metals which tend to change about +0.4%/°C near room temperature.