Software as a Service(SaaS) A Service offering in which the tasks for providing and managing software and sotrage are undertaken completely by the vendor. Ex. Google Apps, MS Office 365, iCloud. Platform as a Service(PaaS) A model that offers a platform on which software can be developed and deployed over the Internet. Infrastructure as a Service(IaaS) A service model that enables organizations to have direct access to their cloud-based servers and storage as they would with traditional hardware. References Champman and Maymi, CompTIA CySA+ exam guild, Mc Graw Hill