Although potentially misleading when applied to bagged baby carrots, the term baby refers to the carrots' size, not their age. Bagged baby carrots are made by taking long, thin carrots (usually carrot varieties grown for their high sugar and beta carotene content, which makes them sweet and bright in color) and forcing them through a carrot-trimming machine that peels the carrots and cuts them down to their ubiquitous baby size.
Real baby carrots, however, are varieties of carrots that are miniature in size when mature; contrary to popular belief, they are not carrots of the standard length that are picked early. Unfortunately, most baby carrots are available only through specialty produce purveyors that sell to restaurants and other professional kitchens. If you are lucky enough to spy true, greens-still-attached, tapered baby carrots in your grocery store or farmer's market, buy them in the cooler months. Baby carrots harvested in the warmer spring and summer months tend to be less sweet and have more of a metallic, turpentine-like flavor.