If you follow business news, you’ve probably heard about activist investor Carl Icahn.

He pushed Family Dollar to sell itself. (Eventually it did .) He pushed eBay to spin off PayPal. (Eventually it did .) And now he’s pushing Apple to buy back more of its stock. (So far, it hasn’t .)

But who is Carl Icahn?

He’s a 78-year-old man worth $23 billion. whose favorite sport seems to be arguing with CEOs.

Activism in general draws a person who does not shy away from the limelight or shy away from a fight, says Scott Galloway, professor of marketing at NYU’s Stern School of Business.

Icahn has been fighting for decades.

Oh, gee, he goes way back, says Donald Margotta, associate professor of finance at Northeastern University.

In the 1980s, Icahn was known not as an activist, but as a corporate raider, using debt to acquire companies, often to break them up.

The  corporate raiders were a little bit different [than today’s activist investors] in that usually their objective was to acquire the company, says Margotta. Whereas now people don’t really want to acquire the company, although they do want to break it up.

Instead of acquiring entire companies, today’s activist investors acquire large portions, and then leverage that portion through the media.

Since activist investors are only taking an ownership position and a portion of the company they also are reliant on other stockholders to have their viewpoint, says Don Steinbrugge, managing partner of hedge-fund consultant Agecroft Partners. The more  media attention they can get the more they can educate the other stockholders in what their position is.

The position could be to buy back stock, to split up the company, to seek an acquisition or a number of other strategies, but the underlying plan is  to rally shareholders to force the CEOs hand, and then profit off any resulting increase in the stock price.

But for Icahn it seems to be about more than making money. He seems to want to set things right — as he sees it.

He basically believes that corporate managers are, by and large, inept and self-serving, Margotta says.

Apple CEO Tim Cook may be the exception. In his open letter. Icahn called Cook the ideal CEO and insisted this letter is in no way intended as a criticism of you as CEO, nor is it intended to be critical of anything you or your team are doing from an operational perspective at Apple.

Except for that share buyback thing, of course.