Manifesto stores a fair amount of detailed debugging information when users are viewing the site. When debugging is enabled in the site preferences (by an Admin), Editors and Admins are able to view detailed debugging information at the bottom of every page on the site.
This information is not visible by normal users, and is harmless, so do not worry if you see it enabled on the site. It allows developers and administrators to get detailed information on database queries, responses, and site configuration settings.
Modules sometimes add their own debugging scripts, such as the Shopping Cart module, to allow for detailed troubleshooting of their operations. Such modules should always configure their scripts to restrict debugging access to editors and admins, to prevent any accidental data disclosures.