CLOUD
Cloud Computing
:A technological approach where computing resources are provisioned in a shareable way, so that lots of usersget what they need, when they need it.
Hardware Virtualization : Physical machine could run many virtual machine instances.
Hypervisor

Infrastructure as a Service (IaaS)
No worries building a new own network or servers
Platform as a Service (Paas)
Subset of cloud computing where a platform is provided for customers to run their services.
Software as a Service (Saas)
A way of licensing the use of software to others while keeping that software centrally hosted and managed.
Ex: Office 365