Cacao v Cocoa
Cacao and cocoa are used so often interchangeably that even vendors disregard any technical differences when naming products. 'Cacao' has traditionally referred to ingredients not processed using heat. 'Cocoa' powder has either been heated or has had ingredients added to transform it into a ready-mix cocoa for drinks or both.
Cacao = natural, more bitter
Roasting helps reduce bitterness and can be employed a different points throughout the production process as a way to soften the bite in cacao's chocolatey flavor.
Alkalization of the cacao will also decrease its bitterness, which is done with a potassium carbonated solution that will neutralize the acidity. This process yields 'Dutched cocoa.' Dutched cocoa is darker in appearance, more soluble in water, and is used in many modern chocolates. NOTE: In baking Dutched cocoa can not be swapped with other powders without accounting for the pH difference. Leavening ingredients in a recipe are usually in proportion to the expected pH of the powder.
Toasting raw cacao nibs in a dry pan for a few minutes can reduce bitterness. Toasting can also add a nutty crunch to the texture of cocoa nibs.
Grinding cacao nibs doesn't produce a powder in the way one might expect. The high fat content (cocoa butter) means that the nibs will become a syrup or "liquor" when ground. Chocolatiers will add more fat, and of course sugar and other ingredients, to this liquor to produce their luxurious product.
To achieve powder from nibs requires extraction of the cocoa butter they contain. The resulting liquor from grinding nibs (mentioned above) is processed using a hydraulic press or similar to separate out the fat (cocoa butter). Though the composition of the nib liquor is about 50% fat, 50% powder; processors will chose to leave between 10-24% of the fat in the powder to improve its flavor and smoothness.