Baking powder and baking soda are two very different things.
Actually, baking powder is made of baking soda, a base, and an acid, usually cream of tartar. Baking soda only reacts and produces carbon dioxide when it is mixed with an acidic ingredient, like chocolate, yogurt, buttermilk, or vinegar. Baking powder produces carbon dioxide when mixed with water.
And there are two kinds of baking powder. Single-acting baking powder reacts just with liquid. You must get the dough or batter into the oven quickly with this type of baking powder, because it starts to lose its leavening power quickly. Double acting baking powder reacts with liquid and also with the heat of the oven. Using this product gives you more leeway in the kitchen.