What is the Boney bump on back of dogs head?

Yes. It is most prominent of your Hunting, Herding, and Working class dogs, and, is there for a purpose. This is for if a dog was to run under a low branch or such, and hit their head, this serves to...

It mean that ur dog is smart that he or her can lean fast

Its the dogs spine.

if the dog is old they're probably warts of cysts. maybe tumors, go to the vet.

Probably just bone that's jutting out though. Ask someone else, though - I'm not sure