If you see a post that has been edited, if you click on the "Edited [Date]" link you will see a list of post revisions. I'll use your question [here](http://serverfault.com/questions/342172/what-is-the-microsoft-loopback-adapter-used-for) as an example.

If you click on the link as shown in the red box:
![enter image description here][1]

You can see (in red) what was taken out and (in green) what was added.
![enter image description here][2]

For more info, have a look at [this](https://meta.stackexchange.com/a/21789/155320) FaQ entry, "How Does Editing Work?"
  [1]: https://i.sstatic.net/MDwWS.png
  [2]: https://i.sstatic.net/QKxnj.png