What a savvy question! Tracking stocks have been in the news a lot recently -- the focus of plenty of press coverage -- yet most investors aren't quite sure what they are so we're glad you asked.

• A tracking stock is a separate class of common stock issued by a company -- usually because the company wants to highlight a particular segment of its business and to "unlock" the value of this business.\

• It's called a tracking stock because it "tracks" the results of the new or separate business.

• Big corporations tend to like tracking stocks because they are a way to bring attention to their fastest-growing sector. That's why quite a few of the newer tracking stocks have been tied to the performance of a company's Internet, high tech or telecommunications business. In your situation, AT&T created a tracker for its wireless business.
  
  Incidentally, in case this topic comes up in a crossword puzzle or you're on a game show, General Motors issued the first two tracking stocks back in the mid-1980s. The one for its EDS subsidiary has since been spun off; the other, for the Hughes satellite division, is still around, trading as Hughes Electronics.

• Tracking stocks are given to current shareholders of the parent company, are sold in the open market in an Initial Public Offering (IPO), or both.

You may wonder why the company doesn't simply spin off its seemingly hot shot division. One reason is that by issuing a tracking stock, the parent company can still maintain control over this division. Another reason is a hoped for positive fallout from publicity. Wall Streets analysts, investment bankers, stockbrokers and the financial press tend to cover tracking stocks -- evaluating them in their firms' reports, in various print and online publications and on the air. With this intensely focused publicity comes the possibility that the stock of the parent company as well as the tracking stock will rise in price.

And, of course, if a tracking stock is launched in an IPO, it gives the parent company a way to raise money. This new source of money can then be used by the parent company to make acquisitions, perhaps pay down debt or even issue stock options to keep or attract key employees.

Is buying a tracking stock a good decision? There is no surefire yes or no answer. It certainly gives you the opportunity to invest in a fast growing segment of a company, but there's no guarantee that it will succeed. As with any stock, if it appreciates in value, you've made a sound decision. But keep in mind, that a tracking stock remains a part of the parent company and cannot be acquired so, never add one to your portfolio with the hope that it will be taken over.

As with all your stocks, monitor your tracking stock carefully. Know your target price. If the stock reaches that level, re-evaluate -- you may wish to buy more shares, sell to cut any losses (hopefully this will not be the case) or ideally, sell to take profits.