I noticed an advert in a "posh" cooking magazine recently. It was for "cacao" and passed off as far superior to common or garden "Cocoa" (and more expensive - about double the price of "ordinary" cocoa).
Don't fall for it. It's just a fancy name for ordinary cocoa.
Having said that, Cocoa is good for you but don't confuse it with "Drinking Chocolate" eg Cadbury's. Drinking chocolate is "got at" with other ingredients whereas cocoa is just cocoa.
Cocoa is said to be a good source of antioxidents (good for us and thought to be good for our hearts). However, it acts as a stimulent so probably not a good idea to drink it as your bedtime drink! And don't let your dog drink it as it may poison him/her (it contains a naturally occuring chemical which is relatively harmless to us but poisonous to dogs).
Try and buy "Fair Trade" cocoa. There is some suggestion that some producers who are not in the "Fair trade" system have been using child slavery on their plantations.
Don’t look for the light at the end of the tunnel. Stomp along and switch the bl**dy thing on yourself.