Types of Cloud Services/Service Models:-

           It reference models on which the Cloud Computing is based. These can be categorized into three basic services as detailed below.

Infrastructure as a service (IaaS):-

                   The most basic category of cloud computing services. With IaaS, you rent IT infrastructure—servers and virtual machines (VMs), storage, networks, operating systems—from a cloud provider on a pay-as-you-go basis.

Example:- Amazon EC2, Windows Azure, Rackspace, Google Compute Engine

Platform as a service (PaaS):-

                   Platform as a service refers to cloud computing services that supply an on-demand environment for developing, testing, delivering and managing software applications. PaaS is designed to make it easier for developers to quickly create web or mobile apps, without worrying about setting up or managing the underlying infrastructure of servers, storage, network and databases needed for development.

Example:- AWS Elastic Beanstalk, Windows Azure, Heroku, force.com, Google App Engine, Apache Stratos.

Software as a service (SaaS):-

                   Software as a service is a method for delivering software applications over the Internet, on demand and typically on a subscription basis. With SaaS, cloud providers host and manage the software application and underlying infrastructure and handle any maintenance, like software upgrades and security patching. Users connect to the application over the Internet, usually with a web browser on their phone, tablet or PC.

Example:- Google Apps, Microsoft Office 365