Amazon Web Services - AWS

Amazon's subsidiary Amazon Web Services (AWS) offers an extensive set of on-demand cloud computing platforms for many IT uses, including computing, storage, networking, database, analytics, application services, and more.

AWS uses an "on-demand concept" for how much you use ("metered"), the level of features you need for the service, the reliability you expect, and so on, which results in flexible costs.

This is very different from charging fixed monthly fees for a certain level of service with usage limits and has proven to be very popular.

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Overview of AWS

Overview of Regions and Availability Zones

Also, check the Infrastructure / Cloud layer topic for an excellent video with an inside view of an AWS datacenter!