Cocoa powder is made from cocoa beans that have been fermented, dried, and roasted before being further processed into cocoa powder. Cacao powder is very similar, except that is has been treated at lower temperatures, which some believe better preserves the antioxidants found in cocoa beans. Both lend a rich chocolaty flavor to whatever you're cooking/baking and it seems they can be used interchangeably.1
Now you might be wondering: then what is dutch process cocoa powder? Dutch process cocoa powder has been treated with an alkaline solution to neutralize the acid present in regular cocoa powder.2 Because cocoa powder will react differently to baking soda/baking powder depending on how acidic it is, you cannot always swap dutch process cocoa powder for regular cocoa powder or vice verse when a recipe includes cocoa powder and baking soda or baking powder. It could be fine, but to be on the safe side, it is probably best to follow the recipe as written.
Nutrition DNA
The nutrition DNA of cocoa powder. For example, you can see that 1 tablespoon cocoa powder covers 10% of your daily need of Manganese and 10% of the recommended Copper intake. Hover over the bars to see which nutrient is covered.