"Explicit sex scenes", in a vulgar description means they show both the penis and the vagina not just boobs and ass. They also show them in a "motion state", by that I mean it is not just a guy standing there hanging out.

The actual motion of intercourse, penetration, stimulation and all the other jazz. In short, for a couple of minutes the movie turns from a regular movie to a porn movie.

Examples: (WARNING: NSFW 18+)
- Ken Park: http://i53.tinypic.com/x22tll.jpg
- Dreamers: http://i56.tinypic.com/4g2i69.jpg