[I really suspect I am doing your homework for you here.]
No camera techniques were used: this is a photogram, where paper is exposed to light directly with no camera, using a point light source far from the paper (quite likely an enlarger stopped right down with no film in the holder). Man Ray was, or at least may have been, the inventor of photograms & made a fairly large number of them. In this case there are at least, I think, three exposures:
- the dark diagonal stripe & dark area on the left is the negative space left by two darkroom trays sitting on top of the paper next to each other.
- there are patterns left by two hands;
- two people kissing have then put their heads over the paper (or possibly one person twice in each direction).
Just searching for it would have found all this information: Man Ray is quite well-known.