Verified CDNs are content delivery networks that are being used by the website as hosting services for their own content.
A content delivery network provides several features, firstly it allows a website to remove load from its web server by moving ancillary files onto another server for them to process, theoretically speeding up the website. Secondly a CDN is normally geographically dispersed to provide a regionally local copy of your data to the recipient. For example, a user in Japan will receive an image from your website from a server in Japan, rather than having to request it from the USA, if that is the original location of the media. CDNs are also suited for large distributions of data; this includes web video and large files as they are better equipped to handle the amount of data being requested.
The most detected CDN by BuiltWith is currently Akamai which are one of the early pioneers of the edge network; geographically dispersed content delivery.