[Pharo-project] What is a primitive method?

Hi all, I have a (basic) question: What is a primitive method? In pharo 1.1.1, we have CompiledMethod>>primitive that basically return: 0 if the method is not a primitive method

0 otherwise

But if you execute this on i.e. Number>>isNumber or Morph>>#model compiled methods you get that these two are primitive methods. Are they primitive methods? Other (related) question is: When I executed the expression: SystemNavigation default allPrimitiveMethods , I get a OrderedCollection with 5581 elements. Are all those methods, primitive methods? Thanks in advance