What is a "Moderated" thread?

In the last two days there has been two threads begun that are labeled "moderated". I have replied to each of these, and although my reply appears in the thread as always, in the "reply" column, there is no record of my reply. These are the only threads I have ever been aware of with this "moderated" label. Can anyone explain what and why this is happening?

Gary,
I have an outside program that looks at posts to see if there is anything wrong with it.
Sometimes it doesn't allow the post, other times it moderates the post.

I haven't figured out what it is that turns it into a moderated post.
Or how to unmoderate it either.