If you haven't been away of the internet for the past few years or if you are an occasional blogger, you must have heard about Markdown. It is a plain text format for writing structured documents. It has been developed in 2004 by John Gruber and widely adopted since then. The problem? A quite ambiguous syntax specification leading to many different implementations. To solve the incompatibility between various implementations, a few engaged folks lead an effort to come up with a common specification called Standard Markdown. This went live last week and got shutdown fairly quickly due to some mood swing from the original author of Markdown. This doesn't matter much, the specification is now live as Common Markdown.
This is a major step forward to help the online community to standardize on Markdown. That being said, there is still many markup formats. If you ever need to convert from one markup format to another, you should check Pandoc or Marksy Chrome Extension.