A repo on PageCDN, just like a zone on any other CDN, is a collection of files that belong to a single origin. An origin can be a push storage (manual uploads), a website, a github repo, or another CDN.
PageCDN uses a single host
pagecdn.io to serve files from all of your repos. One basic use of a repo is to pull content from a website and serve to visitors. But more advanced users can collect content from multiple sources and serve over a single CDN to optimize things.