Cloud Computing has three different service layers that are offered as services.
These three are derived classes of Cloud Computing Services, that depicts the layered organization of cloud stack from physical to application level infrastructure.
1. Infrastructure as a service (laaS)
The first is the infrastructure layer that is developed on virtualization technology where the service providers offer virtual machines as a service to end users. It allows the laaS customers to create and discard virtual machines and networks as per their business requirements. They pay for the services they consumed. It removes the necessity for consumer to invest on procuring and operating physical servers, data storage systems and other networking resources.
2. Platform as a service (PaaS)
PaaS is the second layer. Here the customers do not manage the virtual serves but rather create the applications with in the programming language. They host the programs on platform services which they pay for. The management and maintenance of operating system and other hardware are done by providers.
3. Software as a Service (SaaS)
Applications that do not need to be installed come under this layer. CRMS, email and other office applications come under SaaS. Some services are free while some are billed mothly as per usage.