What is the difference between public cloud & private cloud in salesforce? Is salesforce.com a public cloud or private cloud?

Hello,

Private Cloud
A private cloud hosting solution, also known as an internal or enterprise cloud, resides on company’s intranet or hosted data center where all of your data is protected behind a firewall. This can be a great option for companies who already have expensive data centers because they can use their current infrastructure. However, the main drawback people see with a private cloud is that all management, maintenance and updating of data centers is the responsibility of the company. Over time, it’s expected that your servers will need to be replaced, which can get very expensive. On the other hand, private clouds offer an increased level of security and they share very few, if any, resources with other organizations.

Public Cloud
The main differentiator between public and private clouds is that you aren’t responsible for any of the management of a public cloud hosting solution. Your data is stored in the provider’s data center and the provider is responsible for the management and maintenance of the data center. This type of cloud environment is appealing to many companies because it reduces lead times in testing and deploying new products. However, the drawback is that many companies feel security could be lacking with a public cloud. Even though you don’t control the security of a public cloud, all of your data remains separate from others and security breaches of public clouds are rare.

Thanks.