I am not a sys-admin but a programmer by trade. I know what ESX server is and how it works, I also know and use VMWARE Workstation products.
But what is vSphere? From the marketing material it seems to be something to do with cloud computing. But how does it work? Is it an operating system? Or does it let you run other operating systems within it just like VMWare server or ESX ? How does it work and what need is it supposed to be solving?