Fortune's Most Powerful Women and Yahoo: Keys to success

China's Yang Lan and Avon CEO Andrea Jung

Fortune and Yahoo (YHOO) are teaming up to present weekly content -- stories and videos -- about Most Powerful Women. This is the first in a series of Postcards that will appear on Yahoo and Fortune.com.

It's the start of Most Powerful Women season at Fortune Magazine.

This is the time we begin hunting in earnest for the most successful women in business around the world. Fortune launched Most Powerful Women (MPW) in 1998 when corporate America was the bastion of white men -- white men without facial hair, to be frank. This was a time when the corporate world was clean-cut, prescriptive, and even more conservative than it is today.

We decided to rank, not just list, the MPW because guys, which make up the bulk of Fortune's reader base still, are into rank and status and size. Keeping score, maybe you've noticed, is a classically male thing.

Women are different. We view power horizontally -- it's about making an "impact with purpose," as Oprah Winfrey told me once. Women entrepreneurs, more than men who typically focus on making money, create the companies that they want to work for. Even MPW, our interviews with them show, have had to learn to embrace power. And we still don't love the corporate ladder--which is one reason so many women drop out. We want to use our power to make a difference, broadly.

Over the coming weeks, you'll meet stars of the Fortune Most Powerful Women community, including Avon (AVP) CEO Andrea Jung, McDonald's (MCD) U.S. President Jan Fields and Xerox (XRX) CEO Ursula Burns. And you'll be surprised how many of them are like you and me...

The MPW were not born leaders. But they found something in themselves that enabled them to become great.

Like Anne Mulcahy, who spent her career selling Xerox equipment and never dreamed of being CEO. But when Xerox was on the brink of bankruptcy, she was the one most trusted by the troops, so she stepped up reluctantly, learned finance on the fly, and saved the company.

Xerox CEO Ursula Burns

Like Burns, who grew up in a tenement on New York's Lower East Side, raised by a single mother who told her repeatedly, "Where you are is not who you are." Burns began her run at Xerox as an engineering intern and when Mulcahy retired, she became the first black female CEO in the Fortune 500 history.

And like Jan Fields, who grew up in Vincennes, Indiana, the seventh of eight kids educated in a four-room schoolhouse. Fields went to community college, cooking French fries at McDonald's to pay her way through school. And while she never graduated college, she did just fine at McDonald's. Now Fields is president of the vast U.S. business. Her down-home, inspiring leadership style has earned her the title "the Oprah of McDonald's."

In September, when I interviewed Oprah in Chicago for a Fortune cover story called "Oprah's Next Act," the woman born into poverty to a teenage single mother in rural Mississippi told me that she only recently came to like the word "power" and admit that, yes, she is a brand. "Now I accept that I'm a brand," she told me. "Part of my own personal growth is recognizing that."

I think of power the same way Oprah does: Real power is personal power. It is what you do outside of your official mandate or your job description.

We all have potential power inside us. If you had one extra hour to use your power, what would you do with it?