Despite all the
worthy comments above about "the entire
body blah blah blah", erogenous zones are a
physiological phenomenon characterised by an increased
density of touch-sensitive
receptors in a particular area of the skin.
For some reason these areas tend to be cooler to the touch than surrounding areas (That is practical advice); in my experience when stimulated, they get warmer (not surprisingly), and as the get warmer they get less sensitive.
There tend be a few predictable areas on the (female? I've only researched women's bodies) body where they are found; the only ones I remember from my research are the wrists and the back of the neck.