One of The Six Stats, abbreviated as CHA.
This is the stat that determines someone's ability to influence others. Fairly vague in nature, this influence can take the form of anything from inspiring loyalty to intimidating others, and finds its natural home in checks involving interactions. While usually not explicitly supernatural, the stat can never-the-less even work on supernatural entities in some settings (to the point where it can function like the Polynesian concept of Mana).
Physical attractiveness is a common side effect, although it can also be the main point of the stat, depending on the setting. Sometimes high-Charisma characters having greater presence also translates into resistance against attacks which destroy their sense of self or erase them from reality. The Magnetic Hero and The Heart are natural generators of Charisma, as is the well-written Magnificent Bastard - proof that the fourth wall is no protection against some charm effects. The Face usually has this as their highest stat.
Here's a guide for examples:
12-15: The character is adept at understanding and manipulating other people, though not outstandingly good.
16-19: The character is likely a leader or performer by profession. They have a talent for evoking emotion in others, through speeches, artistic works or possibly just idle taunts.
20-23: The character begins to become more influential than almost anyone has a right to be. A paragon of virtue or brutal dictator are both possible paths.
24+: It doesn't matter how good you are. This guy or gal has several hundred devoted followers to match you, possibly even an entire army or country. Negotiation, bribery, blackmail...none of these will have any effect when matched against raw zeal. It's not like you'll be able to resist for long, anyway.