An excerpt from http://www.sitepoint.com/5-things-you-may-not-know-about-jetpack-for-wordpress/ , by Doyin Faith Kasumu
Jetpack is a popular WordPress plugin created by Automattic, the people behind WordPress.com. The plugin brings many of the most powerful features available on WordPress.com to self-hosted WordPress sites, and thereby contributing greatly to the improvement of WordPress powered blogs and websites.
In this article, I’m going to share five great features of the Jetpack plugin that you may not know about, including how to enable, configure, and use them on your WordPress site.