What is this effect called? Is it film-grain? It kind of looks like but the grains are bigger. Thanks a lot in advance.
This looks very much like monochrome Gaussian (as opposed to Uniform, which it's not) noise at a low opacity. If I were going to reproduce the effect, I'd do this:
Add the noise to a white layer in Multiply or Darken mode @ about 20% opacity above the object. (The example below is in Darken mode at 21%.)
Blend If function (in the Blending Options dialog) to allow the whitest parts of the underlying object to show through.
Film grain is a possible answer.
Another is noise:
You might also try to look up dithering - it's usually associated with GIF compression but can be used in an artsy way.