Most of the medical laser applications were until recently based on the thermal effects caused by the electromagnetic radiation which was absorbed in the biological tissue.

In the last few years, some new applications are using low power lasers with output power less than 1 Watt.

Some of the effects of these low power levels on the biological tissue is not thermal, and in effect the mechanism of interaction is not yet clear.
It is sometimes referred to as Biostimulation, which does not explain a lot.