This effect looks like smoke with a little blurring. There are many examples of this because it has been used in some erotic movies.
I don’t know if it’s a lens filter, a specific camera, a technique, or a type of film. How is this effect achieved?
In the 70s that effect was called 'flu', and was made putting cellophane or similar in the front of the lens.
Some photographers used a plain filter with vaseline or even a piece of pantyhose.
You can do this easy enough in post-processing.
In Darktable the 'bloom' effect would give a similar result, in combination with suitable masks (to limit the area and strenght of the effect, like in the first image). I'm not using photoshop, so I can't give any details for that program.
This is a soft focus effect. As roetnig notes, the effect can be achieved by placing a diffusion filter, or other translucent material, in front of the lens.