What do publish and unpublish mean?

These two terms, "publish" and "unpublish," appear in the development version of askbot. What do they mean?

To be more specific, these terms can be found at

askbot/templates/question/answer_controls.html

in the following lines:

{% trans %}unpublish{% endtrans %} {% else %} {% endif %}

This functionality allows to keep answers private or make them public only when the "groups" are enabled.

All posts are assigned a list of user groups, including group "all" (in which case the post is public), or the list of groups to which the user belongs (either groups where user was assigned by the moderators/admins or the personal user group - where only one user belongs implicitly).

To which groups an answer can be assigned is also restricted by the list of groups to which the question is assigned.