Do I have a WordPress.com-hosted site, or a self-hosted WordPress.org site?
You can read about the difference here: http://en.support.wordpress.com/com-vs-org/
What is Jetpack?
Jetpack is a free plugin that brings many of WordPress.com’s special features to self-hosted WordPress.org sites. For example: amazing photo galleries, infinite scroll, site stats, a server uptime monitor, contact forms, and more.
What will sharing tools do for me?
Jetpack sharing features make your life easier and help your content go further by reaching the people in your networks with minimal effort from you, and those useful, valid links back to your content have the added benefit of being great for SEO.
Where? How? What?