Human capital can be divided into four categories:
(1) Biological capital
(2) Knowledge capital
(3) Track record capital
(4) Social capital
Biological capital includes your innate biological characteristics such as intelligence, sex, age, and health. Biological capital is the only one of the four types of capital which decreases with age. Not only does intelligence decrease with age (after it peaks in your twenties), but your entire body eventually wears out and dies.
Knowledge capital is everything you've learned. As I pointed out in my previous human capital post, most learning occurs on the job and not through formal education.
Track record capital is your track record of accomplishments, including your education (credential capital). It's correlated with your knowledge capital and biological capital, but it's far from a perfect correlation.
Social capital is your acquired social influence. It's who you know.
The former two types of capital, biological capital and knowledge capital, are positive-sum capital. This capital adds to the world's economy.
The latter two types of capital, track record capital and social capital, are zero-sum capital. This capital enables you to transfer wealth from other people to yourself, but it doesn't create value.
If someone earns a massively huge salary (a CEO for example), it's probably because he possesses a great amount of zero-sum capital.
I previously blogged about how worker pay is not based on what the worker is capable of contributing to the economy. This post explains what it's based on: track record capital and social capital.