Intelligence
Intelligence is one of the six Ability Scores used in Dungeons & Dragons, alongside Strength, Dexterity, Constitution, Wisdom and Charisma.
Intelligence is traditionally the "brains" stat, or the "smarts" stat; it represents one's aptitude with reasoning, deduction and logic, as well as one's general state of education and openness to learning and study. The higher your Intelligence, the smarter and more educated you are. This makes it an important stat for an aspiring Skill Monkey, and in 3rd edition, it directly affected how many skill points you gained per level.
Ironically, whilst Intelligence is integral to the Wizard class, whose theme as a studied, educated spellcaster whose power comes from understanding the mechanics of magic itself, it's a popular dump stat for many other classes, especially fighters and other combat-orientated classes. This is because Int usually doesn't have many direct applications to combat use.