·        In cloud computing we talk about various service and deployment models which empowers the need for resource utilization, the most basic and simplest service model is Public cloud. 

·        This is the standard model which followed by cloud computing.  In public cloud the systems and services are easily access to general public for e.g., the mail and storage services offered by google.

·         There are many popular public clouds including Amazon Elastic Compute Cloud (EC2), IBM's Blue Cloud, Sun Cloud, Google AppEngine and Windows Azure Services Platform which offer cloud services via internet.

·         The most salient examples of cloud computing tend to fall into the public cloud model because they are, by definition, publicly available. Software as a Service (SaaS) offerings such as cloud storage and online office applications are perhaps the most familiar, but widely available Infrastructure as a Service (IaaS) and Platform as a Service (PaaS) offerings, including cloud based web hosting and development environments, can follow the model as well (although all can also exist within private clouds)

·         Public clouds are used extensively in offerings for private individuals who are less likely to need the level of infrastructure an security offered by private clouds.

·         Sometimes, Enterprises also utilize the public clouds to make their operations significantly more efficient, for example, with storage of non-sensitive content, online document collaboration and webmail.

Features and Benefits of Public cloud:

High Scalability: Cloud resources are made available on demand from a pool of resources, i.e. they can be scaled up or down according the requirement.

Cost effective: Public clouds bring together greater level of resources and so can benefit from the largest economies of scale. The centralized operation and management of the underlying resource is shared across all of the subsequent cloud services whilst components. Since it shares same resource with large number of consumers, it has low cost.

Utility Style Costing: Public clouds often employs a “pay as you go” charging model whereby the consumer will be able to access the resource they need, when they need it, and only pay for what they used avoiding wasting capacity.

Reliability: Since public cloud employs large number of resources from different locations, if any of the resources fail public cloud can employ another one.

Flexibility: It is very easy to integrate public cloud into private cloud, hence provide flexibility by this approach.

Location independence: For accessing the public cloud facility user just need to have an internet connection, and since the services are delivered from a distributed network, therefore ensures location independence.

Drawbacks:

Low Security: Since the data is hosted off-site and the resources are shared publicly, therefore does not ensure high level of security.

Less Customizable: It is comparatively less customizable then private cloud.