Why are we saying SLUG = FALSE?

The default for slug is FALSE, which means if no slug is passed into the method, it will still be FALSE, which makes the code retrieve ALL articles. If a slug is passed in, like http://yoursite/get_news/some-slug, then it will retrieve the INDIVIDUAL article with the slug that equals "some-slug".

So if you went to: http://yoursite/get_news
it would retrieve all articles because there is no slug provided

If you go to: http://yoursite/get_news/some-slug
it would retrieve the article with the slug of "some-slug"

Kills 2 birds with one stone, so to speak.