It's the point referred to by Master Lin as "the bottom of the torso". Fortunately, Master Lin set up SFQ totally in English, to make it easier. Once I tried to learn 108 points. Too much! Sometimes "areas" are referred to, but those areas have a primary point located in them, and it gets activated or stimulated. The huiyin is center,bottom of the torso, between your private parts. So, when you gently pull up there, you also close those two openings where qi can leak out. Pressing you lips together, again gently, drawing back to the corners of your mouth also amplify holding in the energy. That is from Master Lin too. I think it is a really good added detail to smiling. Being aware of holding in the energy, or storing, I think, is somewhat of an acquired awareness/sensation. As you know, you do drink or eat or bath within 30min of practice, as you absorb the accumululated energy. Another definition of qigong is the "attainment of qi".
