What is the difference between VPS and cloud hosting?

I have tried reading several resources on the internet about cloud computing and VPS but can not see the difference of it. Can anyone explain what is the difference between cloud computing and VPS? IT seems they are both the same as you need to use a virtual machine.

"Cloud" is a marketing term. The actual implementation is what really matters. If you can get detailed info on the architecture of the service provider's cloud you will be able to see who is simply selling you a VPS (such as rackspacecloud) and who is selling you a different implementation that might include failover capabilities as well as other features.