What is intelligence?

What makes something an intelligence? What is the difference between an intelligence and a skill? Support your position

For a long time philosophers tried to find how to measure and define intelligence. Now there are three major theories on intelligence. Charles Spearman proposed the first theory in 1904, where he acknowledged that there are a lot of different types of intelligence and they are correlated. Harvard psychologist Howard Gardner revised this notion with his Theory of Multiple Intelligences, which set forth eight distinct types of intelligence and claimed that there need be no correlation among them. He also stated that a person can posses strong emotion intelligence without being gifted. In 1985, Robert Sternberg, created the Triarchic Theory of Intelligence, which argued that previous definitions of intelligence are too narrow because they are based solely on intelligences that can be assessed in IQ test. Instead, Sternberg believes types of intelligence are broken down into three subsets: analytic, creative, and practical. 

The standard definition of intelligence is the ability to acquire and apply knowledge and skills. It is also a mental ability that involves perceiving relationships, emotions, reasoning, ... etc.  However this definition is way to short and simple and can't just simply define intelligence. Intelligence is a hypothetical idea which we have defined as being reflected by certain types of behavior.

Intelligence is generally understood intelligence to be a combination of biological and environmental (including; diet, parenting style, socio-economic and education) factors. Modern tests focus on spatial ability, reasoning, divergent thinking, and verbal fluency rather than knowledge. 

The Flynn effect refers to the rise of average scores on intelligence tests in most parts of the world over the last century: The average mean scores on standard IQ tests have been going up by about three points every 10 years (Neisser, 1997).Possible environmental factors include better nutrition, improved schooling, better child-rearing practices, increase in financial situation (more books, more toys, better food) and the increased use of technology in modern life. A lot of other studies and research on intelligence showed that brain development is heavily influenced by the environment and this is likely to make an influence on intelligence.
A skill is an ability, coming from ones knowledge, practice aptitude, etc. , to do something well as well as capitative excellence in performance, expertness and dexterity. It is clear that  an intelligence and skills are different. In some way they are also similar, because we gain more intelligence while we develop and grow and we acquire new skills that we didn't have before.