Cloud Storage

Cloud storage is a service model in which data is maintained, managed and backed up remotely and made available to users over a network (typically the Internet).

There are three main cloud storage models:

Public cloud storage services, such as Amazon's Simple Storage Service (S3), provide a multi-tenant storage environment that’s most suitable for unstructured data.

Private cloud storage services provide a dedicated environment protected behind an organization’s firewall. Private clouds are appropriate for users who need customization and more control over their data.

Hybrid cloud storage is a combination of the other two models that includes at least one private cloud and one public cloud infrastructure. An organization might, for example, store actively used and structured data in a private cloud and unstructured and archival data in a public cloud. 

An enterprise-level cloud storage system should be scalable to suit current needs, accessible from anywhere and application-agnostic.

reference 

http://searchcloudstorage.techtarget.com/definition/cloud-storage