The page lets you "review and adjust what data Google uses to personalize your experience, and update what information you share with friends or make public."
You can choose what Google+ profile information you share with others, manage what you share on YouTube, personalize your Google experience by enabling or disabling features like Web & App Activity, Location History, YouTube Search and Watch History. You can also manage ad settings and opt out of ads based on your interests.
All of these features were previously available, but this is a simplified step-by-step guide, just like the Security Checkup. Google wants to make sure you are "always in control of your data and information".