WordPress shortcodes were introduced in version 2.5 and they provides an easy way to publish dynamic contents without requiring any programming skill.
Shortcodes, in WordPress, are macros in the form of  with some functions in it. For example, if you would to embed a YouTube video in your post, you can simply add a string like this to your content:
The result will be
There are a large number of useful shortcodes for various categories like video (YouTube, Vimeo, Vine, Blip.tv), audio (playlists, Spotify, SoundCloud), images and documents (Instagram, Scribd, Office documents) and other awesome things like Google Maps, Gist code snippets or Twitter timeline.
Unfortunately, these shortcodes are available only in WordPress.com (what’s the difference?). It means that they are not available in self-hosted installations of WordPress by default.
To enable them (and other nice advanced features) you have to install the Jetpack plug-in.
Once installed it, you just need to activate it and link the plug-in with a WordPress.com account in order to enable all the advanced features it offers (like Shortcodes obviouly!).
Here is the complete list of Shortcodes.