A VPS is a virtual private server connected to the internet that is running on a larger, real server.
What is Webhosting?
Webhosting is renting (space on) a computer connected to the internet, on which you can run a website.
What is a CDN? And what is a CDN used for?
CDN is an abbreviation for Content Delivery Network and it does exactly what its name says: it delivers content over a network of servers.