Humans are sensitive on parts of their body where they do not have much motor control. The most obvious case is the genitals. Another example is the feet. Most humans have relatively poor motor control over the bottom of their feet, but, for instance, the bottoms of the feet are very sensitive. This form of sensitivity is very important for animals who walk so that they can feel the ground as they walk and thus maintain stability.
Hands have large representation in both the primary motor and somatosensory cortex.
This means that humans have a high degree of sensitivity in their hands as well as the ability for highly coordinated motor abilities. The face also has a large representation in the primary somatosensory cortex. In general, the somatosensory cortex and motor cortex maintain a representation of the human body. The representation reflects the sensitivity or the ability of the body in that domain. Thus, in somatosensory cortex those areas which are most sensitive to touch or to pressure, have the largest representation and those areas of the body which are relatively insensitive have very small representation.