In general, your IQ is a
measurement of how good you are at
IQ tests. These attempt to measure
verbal,
numerical and
logical ability, and obviously your results will have some
correlation with your overall
mental power, but the idea that IQ is some sort of
universal and
eternal benchmark of
intelligence is now largely
discredited.
For example, I was given a "genius"-level IQ at the age of thirteen, but luckily I didn't take this too seriously. When I got to University, it was confirmed to me that the ease with which I could complete puzzles and word games didn't count for much in the real world. Also, although your IQ is supposed to be constant throughout your life (barring brain damage), I am certain that I would not score as highly if I were to do the tests again today, as my brain is out of practice at these sorts of challenges.