g is generally associated with a common conception of intelligence.
g is important in almost every cognitive task studied, including regular daily activities, job perforance, and even reaction time.
The heritability of g is approximately 0.5. Moreover, the heritability of most test performance is primarily a result of g.
Race difference in cogntive test scores tend to be primarily on g. See race and intelligence.
There are many biological and neurological factors that correlate with g. The preponderance of the evidence suggests a biological basis for g.
The exact relationship between g and other factors of cognitive ability is a matter of debate. See the Carroll model.