“The Cloud” refers to software and services that run on the Internet instead of a personal computer. Google’s email service, gmail, runs in the Cloud and is accessible from multiple devices, whereas traditional email systems were software installed on PCs and the messages were stored locally on that machine.
Cloud service providers (CSP) are companies that offer network services, infrastructure, or business applications in the Cloud. The cloud services are hosted in a data center that can be accessed by companies or individuals using network connectivity.
The big benefit of using a Cloud service provider comes in efficiency and economies of scale. Rather than individuals and companies building their own infrastructure to support internal services and applications, the services can be purchased from the CSP, which provide the services to many customers from a shared infrastructure. Also, Cloud systems run as a distributed service, which means that a failure in one datacenter will not bring your own network services down, providing much needed resilience and redundancy.