Earlier, WordPress blogs had lots of nifty features that were available only for the self-hosted sites through a complicated system of levers and pulleys. In order to trick out the self-hosted sites to avail all the features of WordPress, you had to install and maintain dozens and dozens of individual plugins.
But Jetpack is a single plugin that offers you the most powerful WordPress features by clipping your self-hosted WordPress site to WordPress.com’s infrastructure. It allows you to glean all the advantages like easy social sharing, robust stats and a lot more. Read more about Jetpack: WordPress Plugin That Offers Robust Features