Cloud storage is a model of networked online storage where data is stored on virtualized pools of storage which are generally hosted by third parties.
Hosting companies operate large data centers, and people who require their data to be hosted buy or lease storage capacity from them and use it for their storage needs. The data center operators, in the background, virtualize the resources according to the requirements of the customer and expose them as storage pools, which the customers can themselves use to store files or data objects. Physically, the resource may span across multiple servers.
Cloud storage services may be accessed through a web service application programming interface (API), or through a Web-based user interface.