Pt100 thermocouples are a misnomer of two separate types of temperature sensor, a Pt100 resistance thermometer and a thermocouple. Pt100s and thermocouples are two very different technologies both used to measure temperature. A temperature sensor can be one or the other, a sensor cannot be both. It can often be hard to tell if you have a Pt100 or a Thermocouple in front of you if you are not a specialist. Instrumentation can often confused things further. If an instrument accepts both Pt100 and thermocouple input it might be confusingly labelled as Pt100 / Thermocouple.
Some general rules might help you decide if you have a Pt100 or a thermocouple in front of you: