Cloud Storage is a model of data storage in which the digital data is stored in logical pools, the physical storage spans multiple servers, and the physical environment is typically owned and managed by a hosting company. These cloud storage providers are responsible for keeping the data available and accessible, and the physical environment protected and running. People and organizations buy or lease storage capacity from the providers to store user, organization, or application data.
Cloud storage services may be accessed through a co-located cloud computer service, a web service or by applications such as cloud desktop storage or content management systems.
(Subject to revision as this layman poster learns more!)