Intelligence refers to intellectual functioning.

What exactly is intelligence? British psychologist Charles Spearman believed intelligence consisted of one general factor, called g, which could be measured and compared among individuals. IQ—or intelligence quotient—is the score most widely used to assess general intelligence or "g," and typically measures a variety of skills from verbal to spatial. The way that researchers have defined the concept of intelligence has been modified many times since the birth of psychology.
Human intelligence, mental quality that consists of the abilities to learn from experience, adapt to new situations, understand and handle abstract concepts, and use knowledge to manipulate one ’s …

These tests don’t measure all kinds of intelligence, however. In psychology, intelligence is a mental quality that includes the ability to think, learn from experience, adapt to new situations, apply knowledge and solve challenges and problems. Intelligence quotients, or IQ tests, compare your performance with other people your age who take the same test.