A special interest of mine is working with gifted children and adolescents, both as a therapist and as someone who does IQ testing. I practice in a school district in Illinois (District 220) that has a phenomenal program for gifted youth. Gifted, in this context, means having IQ test scores in the 5th percentile.
The label "gifted" can be very controversial. What parent doesn't think s/he has a gifted child? Isn't every child gifted in some way? Doesn't labeling some children as gifted an elitist notion that denies all children equal educational opportunities? These criticisms have at times contributed to a reduction or absence of funding for gifted and talented programs. It also must be noted people are not simply "born gifted." Children from economically disadvantaged communities are subject to a wide range of factors limiting the development of their IQ, sometimes starting in the womb.***
The reason I think it can be helpful to identify some children as gifted is because of their unique needs, not only intellectually but emotionally. These children can get bored in a normal classroom, contributing at times to behaviors that can mimic ADHD, such as daydreaming and restlessness. Emotionally, it is not always a gift for things to come easily. What happens when that child comes across something that is difficult to do? Many gifted children struggle with perfectionism. Another common challenge for these children is finding peers that are interested in the same things, leading sometimes to feelings of isolation and even inferiority.
Paradoxically, no matter your child's IQ, it does not help to focus on the idea that they are smart. In his book How We Decide Jonah Lehrer reviews some fascinating studies supporting the idea that success comes from the willingness to persist and to learn from our mistakes. Interestingly, children who identify as "smart" may fear losing that "smartness" every time they find a task difficult or do not get the "right" answer, leading them to avoid difficult tasks and ultimately learn less. In contrast, it is good to praise your child for effort and for trying again when they face obstacles.
*** In her book Origins, Annie Murphy Paul does an excellent job of reviewing recent studies of the impact of the prenatal environment on a wide range of factors, including IQ.