This is a PIR based motion sensor, so uses passive infrared to detect motion. PIR sensors are known for their high accuracy, with the ability to detect even still occupants based on their breathing.

A device used to detect motion by receiving infrared radiation. When a person walks past the sensor, it detects a rapid change of infrared energy and sends a signal. PIR sensors are used for ...

As an example, [Circuit Valley] has an IKEA Vallhorn motion sensor for a teardown, it’s as you might expect, a passive infrared sensor (PIR) sensor coupled with a Zigbee interface. Inside the ...

The wireless DUAL TEC® motion sensor provides faster and more reliable detection using K-band microwaves to quickly verify the PIR signal prior to any alarm ... from a faster installation using ...

Most of us would probably expect to see a PIR sensor, but this light is motion sensing with microwaves. We have seen such units tested in the past, which links to a video [hclxing] also references.