A short definition
IQ stands for Intelligence Quotient. It is a single number that summarises how a person performs on a standardised test of reasoning, compared to a large reference population of the same age. By construction, the average IQ is 100, and about two thirds of people score between 85 and 115.
Crucially, an IQ score is not a measurement of a fixed quantity in your brain. It is a statistical position: it tells you where you sit on a distribution at one moment in time, on one type of test, under one set of conditions.
What IQ tests actually measure
Modern IQ tests probe several distinct abilities: fluid reasoning (solving new problems), crystallised knowledge (what you have learned), working memory (holding information in mind), processing speed, and visuospatial reasoning. The Cattell–Horn–Carroll model — the dominant framework in psychometrics — describes more than a dozen of these narrow abilities under a single general factor called 'g'.
Most online IQ tests, including ours, focus on fluid reasoning through visual matrices. Matrices are useful because they are largely culture-free and language-free: you do not need to know any particular vocabulary or have studied any particular curriculum to solve them.
What IQ doesn't measure
An IQ score does not capture creativity, emotional intelligence, social skill, motivation, grit, ethical judgement, or practical wisdom. People with very high IQs sometimes struggle in life; people with average IQs often achieve extraordinary things. The number is informative, but it is not a verdict.
It also does not measure your potential. Cognitive abilities change with sleep, stress, nutrition, education, and practice. A score taken on a bad day, or after months without mental stimulation, will under-represent what you are capable of on a good day.
How to interpret a score
A useful way to read an IQ score is as a percentile. A score of 115 means you scored better than about 84% of the reference population on that test. A score of 130 corresponds to roughly the top 2%.
Differences of less than 5 points are usually within measurement noise. Differences of 10 points or more typically reflect real variation in the abilities being tested.