Ruby on rails help!

Can someone enlighten me about

    * Public Instance Methods.
    * Public Class Methods.
    * What is the root class for all Ruby Classes if there is one.

Can someone enlighten me about

   * Public Instance Methods.
   * Public Class Methods.

as in what's the difference? instance methods are methods you call on
an instance, class methods are ones you call on a class.
For example if Person is an ActiveRecord model then Person.find is a
class method, but save is an instance method, ie some_person.save
where some_person is an instance of Person

   * What is the root class for all Ruby Classes if there is one.

Object

Fred