An Intelligence Quotient indicates a person's intelligence depending on that person's age. The term "IQ" comes from the German "Intelligenz-Quotient".
There are many benefits of knowing your IQ. For starters, by taking an IQ test you will know in what areas of intelligence you excel and in which ones you're average or below average. Many employers ask their employees to take an IQ test, so knowing your IQ in advance can be an advantage. Additionally, by knowing your IQ you can work to improve it.
Many people think that IQ tests are very limited. However, there is plenty of evidence to support otherwise. A high IQ test highly correlated with academic performance, musical talent and many other traits. Some IQ tests (such as the one on this website) also measure other areas of the brain like social intelligence and language proficiency.