On Premise
Infrastructure
- You have to buy your own Hardware (Physcial Servers)
- Have a place to put all these servers + Pay for Physcial Sercurity
- Pay for electricity and cooling
Platform
- Buy Operating Systems (Unix or Windows)
- Install OS + Maintain/Upgrade your OS with it's patches
- Install basic software like Java and other libraries to run
Apps (Application Software)
- Install your SAP or PeopleSoft or Custom Built Software
- Maintain/Upgrade your Software

vs

Cloud Computing -- (IAAS - Infrastructure AS A SERVICE) or (PAAS - Platform AS A SERVICE) or (SAAS - Software AS A SERVICE)