VPS hosting contains the best elements of shared hosting and dedicated hosting services. Like shared hosting, VPS hosting puts your website on a server that also has other sites running on it, except that there are fewer sites per server. The sites share the cost of running on the server, which results in a monthly or yearly charge that's less than the relatively high price tag of dedicated hosting.
A Content Distribution Network (CDN) is a network of servers distributed geographically. The purpose of a CDN is to deliver content on the internet much faster. If a user in Toronto is trying to access your website, the closest server to them will take care of this. But someone coming to your website from Sydney, Australia, will be catered to by a server closest to them. The main host server holds your website content, and all the other servers have a cached version each.