All of them will be shown step by step. This refers to the change in resistance as a function of temperature. See my previous article for a graph.
Manufacturers publish graphs and tables.
Standardized Resistance-Temperature Curves. One can manufacture NTC thermistors that, when the rated resistances are normalized, have the same, standardized temperature-resistance characteristics. This is very convenient since instead of dealing with a resistance-temperature curve for each individual thermistor, one now has classes of thermistors. As the current increases, the self-heating causes the resistance to decrease even more. This is the part of the slope where the graph has a negative slope, and is the negative- resistance region of the thermistor.