According to my knowledge cloud computing centralize the common resources so that it is easy to share it. Resources we're here meant by servers ..Am i correct? please correct me if i am wrong...
According to what I have understood: Its on demand service- Be it hardware or software resources. So we have Software as a Service(SaaS), Platform as a Service(PaaS). So the cloud takes care you your computing needs- You just have to specify your requirements. Good examples of this are- Amazon Cloud, Salesforce (SaaS), even Google with its Google Apps.