[ruby] what is this code doing

What is the "self"? It is not defined anywhere in the example. What does .call mean? It looks like it is returning an element in an array here. Is this correct?

class Array
 def eachEven(&wasABlock_nowAProc)
   even.
    isEven = true

    self.each do |object|
      if isEven
        wasABlock_nowAProc.call object
      end

      isEven = (not isEven)  
    end
  end 
end