I guess you get all your spent skillpoints back and reset your skills
Which brings me to a question: Later you can unlock the "Megacoin". I unlocked it, but I am not sure if the first skill "increase your tapping coin power" works for the Megacoin too.
Would be great to get a 10x Bonus on the megacoin. But if it doesnt stack, I see no point in investing in the tappingpower, because it gives so little money... :/