An -EX, which stands for Explained, SCP is one which we have figured out. It is an SCP that is no longer an SCP, either because it has become common place, we worked out the rules behind it, or that it has just become a complete non issue.
The difference between a regular SCP and an SCP-EX are, mainly, three. First, the -EX designation. Any SCP made as an -EX needs to have a page title of SCP-###-EX. Second, the containment protocol. While I would still like to see the old containment protocols, perhaps striked out, -an EX no longer needs to be contained, for whatever reason. And, number three, at the end of the article, there needs to be a section detailing HOW it went from normal to -EX.
For more information on what an -EX SCP is, please check out the full forum thread. If you write one, please link your -EX articles here so others can see your work!