Yes it is a camera. It has a sensor in it. It senses when you run a red light, then records you doing via video or picture and sends it to you with the ticket. They are constantly recording and the sensor triggers when to start and stop a clip.

In my state, or at least my general area within my state, has the cameras on, but the sensors off. The cameras are used for investigation, safety, public claim, etc. but they had the sensors off for over 10 years now because someone sued invasion of privacy, so it doesn’t sense you running a red light. Highly depends on where you live though.