A Puck that is configured as a "Sensor".
A Sensor Puck reads temperature and will send IR commands when paired with an IR device (mini split, window AC, portable heaters, etc.)
A Sensor Puck runs on batteries, and can optionally be plugged into AC power.
A Sensor Puck will briefly connect to WiFi during Setup when downloading codes for an IR Device it's paired with - or when installing an update.
Otherwise, Sensor Pucks are not connected to your home WiFi, but instead use the Flair Network to communicate with Gateway Pucks.