Cloud Hosting" has been creating quite a buzz around these days. You might be hearing the phrase for the first time but the technology is not something new at this time of writing.
"CloudFiles proves to be a simple and easy to use
way to store files in the internet and distrubute them for performance or high-availability ( or both )"
-Matthew Sacks, The Bitsource
SaaS is one of the methodologies of Cloud Computing, which is based on a "one-to-many" model whereby an application is shared across multiple clients.