Baking powder is a leavening agent. You’ll most often use baking powder when making baked goods that need some rise. Baking powder and baking soda are not the same product.
If you’re all out of baking powder or simply want to use something different- there are quite a few alternatives you can use. Most of which you’ll already have in your pantry.
Another handy replacement is cornstarch – which you probably already have in your pantry as gluten intolerant. You’ll need 2 parts cornstarch, 1 part baking soda, and 1 part cream of tartar.