Infrared Sensor §

I remember seeing these IR Sensor when first learning Arduino https://www.amazon.ca/Geekstory-HC-SR501-Pyroelectric-Infrared-Modules/dp/B07X31RVJY/ref=sr_1_13?keywords=infrared+sensor&qid=1673300787&sr=8-13

Passive Infrared (PIR) Sensor §

I think those are the same thing, except they are lower energy?