Why does my iPhone 7 have a laser?

In the box of my iPhone 7 there was a leaflet with all sorts of small print easy enough to be dismissed as some legal document (and maybe it is). I couldn't help reading it and on the reverse page it says something about Class 1 Laser Information: See text: "This device contains a laser"

So my question is where in the iPhone and, more importantly, for what purpose is the laser in the iPhone?

This site indicates that the front facing proximity sensor consists of the laser and filters to attenuate the signal to safe levels once assembled.

Located in the front of the phone, above the main speaker, the FlightSenseTM proximity sensor uses optical land-grid array (LGA) packaging. The custom Apple device measures 2.80 mm x 2.40 mm, half the size of the rest of STMicroelectronics’s portfolio.

That reinforces the warning about repair and implies potential danger if you operate the components while the iPhone is disassembled.