What is a reference cycle in python?

Question

I have looked in the official documentation for python, but i cannot seem to find what a reference cycle is. Could anyone please clarify what it is for me, as i am trying to

Answer 1

>>> x=[1,2,3]
>>> x.append(x)
>>> x
[1, 2, 3, [...]]
>>> 

Now here variable x is referring to itself, this is called reference cycle.