Jetpack’s Related Posts feature scans all of the posts on your site (or blog), analyzes them, and shows your visitors other posts with related content that they might be interested in reading once they’re done reading the one that brought them to your site.
Most sites who activate this see an increase in traffic. On this site, Jetpack.me, when we compare pages with and without the feature enabled we see around 79% more visitors clicking through to one other post on the site.

This data is based on a 6-month traffic comparison between blog posts showing related posts and pages with the feature disabled. Turning on the feature for us in essence means that almost twice as many visitors read something else besides the original post that brought them here.
How does it work?
The related content is automatically generated based on the content of the post and any tags or categories if they exist. Unlike many other related post plugins, we do all the analysis, processing, and serving from our cloud, so there is no additional load on your server. (That’s why many plugins like YARPP or Similar Posts are often banned by web hosts, but Jetpack Related Posts are allowed.)
This is not unlike other Jetpack features like Photon and Stats that rely on our cloud infrastructure for the heavy lifting.
Once its enabled (and if you have more than 10 posts in total on your site) the related posts will show up in a “Related Posts” section just below your main post content, very much like what you can see at the bottom of this post 🙂
How to enable it
First, you need to have Jetpack installed and connected to your WordPress.com account.
Once this is done, go to the Jetpack page in your blog’s dashboard and click the Activate button for Related Posts. You can also customize how the related posts section looks by going to your Settings → Reading page and scrolling down to the options next to “Related posts.”