The range of temperatures over which the thermistor can operate effectively.
They can be used to compensate for temperature variations in electronic circuits.
Given the ambiguity, I'll provide a general guide on how to approach a datasheet review for electronic components, which you can apply to the "HX-JE Datasheet":
When looking at the datasheet for the HX-JE or similar NTC thermistors, here are some key parameters you would typically find: