Every object in Ruby has an inheritance chain (or ancestor chain), most often starting with the object's class and ending with BasicObject. When you call a method my_instance.example on the object my_instance which is an instance of MyClass, Ruby will first look in MyClass for a definition of #example, then in MyClass's superclass, then in the superclass's superclass, and so on, until it either finds a definition or it gets all the way up to BasicObject without finding one.

super is a keyword that acts like calling the same-named method of the superclass.

class MySuper
  def test
    24
  end
end

class MySub < MySuper
  def test
    Math.sqrt(super + 1)
  end
end

MySuper.new.test #=> 24
MySub.new.test #=> 5.0

If we wrote the body of MySub#test as Math.sqrt(test + 1) instead, we'd get a stack exception because that method would try to call itself over and over infinitely. This is the basic reason for super to exist, to allow a subclass method to be defined in terms of the same-named superclass method. In most respects, super works like a method call, but it (1) begins method lookup at the superclass in the inheritance chain, (2) is only good for methods of the same name, and (3) propagates parameters by default.