It's Public or Private
It's on demand
In simple, uncomplicated terms, cloud computing allows you to store and access data via the internet instead of the traditional way of your computer’s hard drive. The term "cloud" simply stands as a metaphor for the Internet. In fact, you might have come across many "cloud" symbols before, as it is often used to portray the Internet on diagrams and other illustrations, and if you use online services such as Gmail, Facebook, Netflix or Spotify, you will be using a cloud system already.
Types of cloud computing
IT people mostly talk about three different kinds of cloud computing:
⮚ IaaS (Infrastructure as a Service) Could be referred to as utility computing or the most "basic" model of cloud computing. It is often a pay-as-you-go solution, providing access to raw computing hardware over the Internet through purchasing services as a computing infrastructure. A monthly fee usually needs to be paid per subscription or as per-megabyte/gigabyte to a hosting company. In this model, the cloud user maintains the operating system and the application software.
⮚ SaaS (Software as a Service) A complete application is usually used running on an external system. Users gain access to the application software and data, and Cloud providers manage the infrastructure and platforms that run the application. The SaaS model is sometimes also referred to as on-demand service and usually on a pay-per-use or subscription fee basis. Cloud providers install and operate the application software while the users access the software from cloud clients (typically s standard web browser). Cloud users do not manage the infrastructure or platform where the application runs, therefore eliminating the need to install the application on the user's own computer, simplifying maintainance and reducing support or service costs.
⮚ PaaS (Platform as a Service) Allowing the development of applications using Web-based tools so they run on systems and hardware provided by another company. This typically includes operating systems, programming-language execution environment, database and web server, allowing developers to develop and run their software solutions on a cloud platform without the cost of buying and managing the underlying hardware and software layers.
⮚ Private Cloud Also called the internal Cloud, the private cloud offers a platform that is implemented on a cloud-based secure environment that is safeguarded through a firewall which is under the governance of the IT department of the parent organisation. One of many advantages might be that Private Cloud offers the organisation greater and more direct control over their data. Whether the physical computers are hosted internally or externally, resources are provided from a distinct pool for each customer organisation.
⮚ Public Cloud When the cloud services are provided from resources that are open for public use, it is called a Public Cloud. The customers do not have any control over the location or nature of the infrastructure, outside of the options provided by the cloud provider. From a technical point of view, there might be little to no difference between private and public clouds' structural design, and even less distinction from the view of an end user.