The term IQ is short for intelligence quotient and is a number that says how smart you are.
Google's definition is: a number representing a person's reasoning ability (measured using problem-solving tests) as compared to the statistical norm or average for their age, taken as 100.
Short rant about the tests below
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However, it has been shown that these tests don't show much intelligence at all as they were invented in 1904 to see if French children were doing well in Kindergarten. Some other early tests were biased towards rich white males. Both of the most popular tests, the Stanford-Binet and the Weschler, can give very different results from each other.
In reality, there is no way to standardize human intelligence.