1. Personality (The higher your Charisma, the more dynamic your personality is)
2. Personal Magnetism (Ability to draw others in)
3. Ability to lead (Ability to inspire others)
4. Appearance (Grace)
5. If 0, you may not exert yourself (not quite sure how this distinguishes from the other scores being at 0)
So, according to the book, what is Charisma NOT
2. Your ability to use magical items
3. Most creatures ability to cast SLAs
4. A Sorcerer's, Bards, Paladin's, Summoner's, and Oracle's ability to cast spells
5. The Ki-Pool of a ninja
6. The duration and effectiveness of a ninja's, paladin's, and a bard's abilities
7. A Druid's and a Hunter's ability to influence animals
8...... the list goes on
Charisma, not per the dictionary, but as I see it applying to Pathfinder, measures Self-Actualization as well. Now, while this seems much more appropriate for Wisdom, but the Paizo definition of Wisdom refers almost exclusively to one's interaction with their surroundings, and with information.
Now, when I say Self-Actualization, I'm referring to the idea of someone working toward understanding themselves, and reaching their full potential. For example, why do spontaneous casters and SLA's (primarily) depend on Charisma? Because it requires the creature to be in touch with what they are innately, what it is they have inside of themselves. They need to understand what's inside of them before they can adequately express it externally, in this case, Magic.
Now lets apply this same principle to the idea of "personal magnetism", it's the same thing. Understanding your potential, and who you are gives you a significant advantage in your ability to influence and inspire courage in others. After all, what wise man ever truly believed in someone who did not believe in themselves?
Now, a bit more of a stretch, how could Charisma possibly enhance your AC? The way I look at it, it can be interpreted as follows: a creature with a high Charisma can channel their self confidence and self understanding into a physical advantage in combat. After-all, there is nothing more attractive than a woman who is not only physically sexy, but who is confident in her... own assets. Regardless of how "hot" or fit her body is, she cannot reach her full potential (physically) if she does not understand what it is she is working with, and isn't confident in what that is. Another example would be a man stepping into a yoga class. It takes a special kind of confidence for a man to get himself to move like that. Even individuals who aren't perfect physically, but are confident and comfortable with who and what they are are better company than shallow or insecure individuals.
Anyway, I've been working a melee class which incorporates some of these ideas, such as "AC Bonus" as Monk but with Charisma instead of Wisdom, bonuses to social skills, bonuses to certain acrobatics or escape artist rolls, charisma-based abilities that help you push a physical ability to the next level.