
- SaaS (software as a service)
- PaaS (Platform as a service)
- IaaS (Infrastructure as a service)
Software as a service - SaaS
SaaS s a software that is centrally hosted and managed for the end customer. It is usually based on a multi tenant architecture - a single version of the application is used for all the customers. It can be scaled to a multiple instances to ensure the best performance at all the locations. SaaS Software is typically licensed through a monthly or annual subscription.
Example :- Microsoft Office 365 is a prototypical model of SaaS. Other example are Dropbox,WordPress and Amazon Kindle.
Platform as a Service - PaaS

Infrastructure as a Service - IaaS
An IaaS cloud vendor runs and manages server farms running virtualization software, enabling you to create VMs (Virtual Machines) that run on the vendor’s infrastructure. Depending on the vendor, you can create a VM running Windows or Linux and install anything you want on it.