What is Cloud?

There is still a debate among some IT experts on definition or understanding of Cloud and how it differ from offering software as service. So what I've decided is to give an overview of cloud offering and its layer in simplest way possible. First, understand its defintion - Cloud computing is delivery of computing as a service, where shared resources, software and information are provided to computers and other devices as a utility (like electricity) over a network (like grid station which product electricity or internet) so it is service delivery platform.

Now, there're 3 major layers of Cloud computing. Today, I will just explain these 3 layers briefly.

Application Layer: Software as a Service (SaaS), sometimes referred to as "on-demand software" is a software delivery model in which software and its associated data are hosted centrally (typically in the (Internet)  and are typically accessed by users using a thin client, normally using a web browser over the Internet. SaaS has become a common delivery model for most business applications, including accounting, collaboration, customer relationship management (CRM), enterprise resource planning (ERP), invoicing, human resource management (HRM), content management (CM) and service desk management.

Platform Layer: Platform as a Service (PaaS) is a way to rent hardware, operating systems, storage and network capacity over the Internet. The service delivery model allows the customer to rent virtualized servers and associated services for running existing applications or developing and testing new ones.

In other words, PaaS is the delivery of a computing platform and solution stack as a service. PaaS offerings facilitate deployment of applications without the cost and complexity of buying and managing the underlying hardware and software and provisioning hosting capabilities, providing all of the facilities required to support the complete life cycle of building and delivering web applications and services entirely available from the Internet. So you're also using platform for software development.

PaaS offerings may include facilities for application design, application development, testing, deployment and hosting as well as application services such as team collaboration, web service integration and marshalling, database integration, security, scalability, storage, application versioning, application instrumentation and developer community facilitation. These services may be provisioned as an integrated solution over the web. It facilitates deployment of applications without the cost and complexity of buying and managing the underlying hardware and software layers

Infrastructure Layer: Infrastructure as a Service is a provision model in which an organization outsources the equipment used to support operations, including storage, hardware, servers and networking components. The service provider owns the equipment and is responsible for housing, running and maintaining it. The client typically pays on a per-use basis.

Characteristics and components of IaaS include Utility computing service and billing model, automation of administrative tasks, dynamic scaling, desktop virtualization.

• So if you're offering software as a service - it's SaaS, where your customer come and use these software as an hosted offering.
• Now if you add a platform, where developers, community contributors come and use this platform for development, maintenance, testing etc. of any deployed software then it's PaaS. 
• And if you also add hardware in your cloud as service then it's IaaS like block storage, network.

Hope, it was helpful... I will be explaining all these terms in detail in coming posts.