Jetpack contains a wide array of modules that help you to customize, secure and keep track of your WordPress site. There are too many for all of them to be listed here, and more are added at a steady clip, but these are some of the more prominent ones:
- Comments: Replaces the default WordPress comment system with one that allow visitors to log in and comment with their accounts on social media, like Facebook.
- Contact Form: A simple way to add contact forms to your posts and pages.
- Infinite Scroll: If it’s supported by your theme, this function will load new posts on your archive pages without doing a hard reload of the page.
- Lazy Images: Images will only be loaded from the server when they’re actually visible on the page, which reduces the load times.
- Protect: This module helps make your website safer by protecting it against malicious login attempts and denial of service attacks.
- Sharing: Displays sharing buttons for social networks in the bottom of posts. You can customize which networks to include and the presentation of the buttons.
- Site Stats: Displays visitor statistics for your website. It isn’t as feature complete as Google Analytics, but it’s a pretty good lightweight alternative.
You don’t need to have all of these modules active if you have Jetpack installed. You could, for instance, deactivate everything but Site Stats and only use Jetpack to track visitor statistics. You do need to have an account on WordPress.com to use most of the modules, though.
There are standalone alternatives to almost all of the modules included in Jetpack, but having them collected in a single plugin has its benefits. If nothing else, you know that you can trust the developer to keep it maintained and supported. Jetpack is developed by Automattic, the company running WordPress.com.