What does "oneboxing" mean in Discourse?

Taken from https://meta.discourse.org/t/what-is-a-onebox/4546 (now offline)

One very cool feature Discourse has is "oneboxing". If you include a link to your favourite site, it will try to create a usable snippet for you automatically. For example: paste the link http://en.wikipedia.org/wiki/Spite_house on a line by itself and you will see a nice onebox from Wikipedia Some samples:




also see https://github.com/discourse/onebox