First, it can refer to a child's higher degree of giftedness in one area. Typically, we refer to a child as being verbally gifted or quantitatively gifted. To a lesser degree, you hear of a child's spatial giftedness. Often, you see a child with particular acuity at math or language. You then see the child having a weakness in the reflexive area. We also see evidence of gifted children having learning disabilities in their weaker area. This is usually referred to as a child being "twice-exceptional". Many scholars and researchers believe that the greater the skill in one area, the greater the deficit will be in the other area. It is almost as though the scales are trying to balance themselves.
This could happen for a variety of reasons. Gifted children tend to shy away from their weaknesses. We like and are successful at that which comes easiest to us. We tend not to like the tasks which are most difficult for us. In my current self-contained program, you only need to be in the 97th percentile in one area to qualify, because we feel that you can learn to be stronger in your weaker area. You have the potential to be successful in many areas if taught the right coping skills and learning strategies. We have seen tremendous growth in students with this ideology.
There is also research which indicates that the brain actually demonstrates more activity in the strength regions and less in the weaker regions. It could be that some people are just better at certain tasks. Our brains may just be wired for specialization.