What is Cloud?

The best explanation i have found online is

In the beginning of PC computing, all applications were run from (and data was stored on) each individual system's local hard drive. As time went on, companies recognized the benefits of centralized management and control and moved to a model where data is stored on, and many apps are run from, servers on the local network. The next step will move apps and data storage even farther away from the end user, into the "cloud," with everything residing on remote servers accessed via the Internet. This will allow users to access those programs and data anywhere, from any Internet-connected machine, including low-powered (and low-cost) netbooks

I talk more about 2 of the main cloud provider here Azure and Aws