It is the mapping of your body onto your brain, or, in more technical terms, it is the cortical homunculus - the somatosensory representation of the body upon the surface of your cortex.
The picture shows a front-on view of your brain, and how your body is mapped upon it - at least according to the first mapping published in 1950 by Wilder Penfield, and Theodore Rasmussen.
Penfield produced this image by electrically stimulating the naked cortex of patient's brains. Not for kicks, mind you, but to identify what-was-connected-to-what prior to surgery. So that he knew what parts of the brain he could and could not muck about with.
You may have noticed, for the sake of modesty, that the genitals are not displayed. And, according to Penfield and Rasmussen, the genitals are not located where you would think they would be (at the pelvis) but just below the toes!
Foot fetish anyone?
Even more interesting, subsequent research by Vilanyur Ramachandran, in his book "Phantoms of the Brain", has described peculiar cases of amputees who have lost legs. The cortical area which formerly processed input from the feet and toes were taken over by the genitalia. In other words, all the little neurons that used to process sensations from the feet were co-opted to process sensations from the genitalia. Even more interesting, such amputees would often experience the pleasure of an orgasm not just in their naughty bits, but in their toes, feet and sometimes the whole leg!
Subsequent investigations, in such papers with such erotic titles as "Sensory Cortical Representation of the Human Penis: Revisiting Somatotopy in the Male Homunculus", indicates that the sensory areas are actually spread out over different areas of the brain, and that the main sensory location for the penis actually lies laterally next to the big toe (not below it).
Something to explore in your off-hours, I suppose.