Yeah, this is exactly what I'm wondering about - I understand the big picture and have done my homework on Cloud Computing, but Cloud Hosting, is something I've never heard before. Sure, I understand the concept, but how does it work behind the scenes? How do you enable it? How do you setup?
Most of the terminology around cloud computing is still very loosely defined, with many companies's CTOs, like Oracle's, saying it's just relabeling something that has already been around for a while.
I just did a search for the term "Cloud Hosting" and best I can tell it's a subset of Cloud Computing covering these common cloud services : cloud web servers, cloud storage, and cloud load balancers. Essentially the web/file hosting portions of cloud computing, so it would exclude things like MapReduce which is for tackling large distributed processing tasks.
So Amazon's EC2, load balancer and S3 would be included. Possibly, Simple DB or Cloud Front... I don't know enough about Google's App Engine or Saleforce.com to comment one which of their services would count.
BTW, the cloud manifesto is an attempt to better define what cloud computing is. http://opencloudmanifesto.org/Cloud_Computing_Use_Cases_Whitepaper-2_0.pdf But even it is a work in progress, which doesn't mention the term cloud hosting. But take a look at the IaaS and PaaS sections to see if these helps you.
Good luck...