What is meaning of '[::1]'?

From
https://docs.djangoproject.com/en/1.10/ref/settings/#std:setting-ALLOWED_HOSTS:

"When DEBUG is |True| and |ALLOWED_HOSTS| is empty, the host is
validated against |['localhost', '127.0.0.1', '[::1]']|."

What is meaning of '[::1]'?

--
You received this message because you are subscribed to the Google Groups "Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscribe@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at https://groups.google.com/group/django-users.
To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/02858789-fa42-f8fe-817f-94360b3ddd7d%40gmail.com.
For more options, visit https://groups.google.com/d/optout.