What is Cloud Computing?

Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. - US NIST

Basically, it is a metaphor used for the group of networked resources, managed by a service provider. Customers avail these services as their requirement without taking any stress of management and maintenance of the infrastructure.

Five fundamental attributes of Cloud Computing are:

1. On-demand and Self service: Customer gets the resources on-demand and these resources are self-served. No human intervention is required as Cloud Providers provides the automated interfaces.
2. Globally Accessible: Since these resources are connected over the broad network, they can be accessed remotely.
3. Resource Pooling: Multiple customers share the resources. Customers don't need to care about the location, maintenance of resources.
4. Rapid Elasticity: Resources are provided rapidly if requirements increase. Similarly, resources are scaled-down when not required.
5. Pay as you go: Rapid Elasticity helps to reduce the cost of using the resources, customer needs to pay only what he/she reserves or use.