The cloud computing market is dominated by some familiar names.

Amazon's cloud service is its most profitable unit. Microsoft has pegged its future to its cloud computing businesses, leading to a very enthusiastic response from Wall Street. Google, too, is betting big on cloud computing as something that could be bigger than its advertising business.

What exactly are these companies selling? Who's buying it? And why is one company that wasn't even in enterprise technology a decade ago — Amazon — beating the pants off everyone else?

Here's the state of play in the cloud game.

Why everybody's going to the cloud

The most important concept in cloud computing is "hyperscale."

To support their own websites and services, Amazon, Microsoft, and Google have all built a ton of computing infrastructure. Their data centers are vastly bigger — and way more efficient — than those operated by or could be built by most other companies.

For years now, these giants have rented out some of their computing capacity to developers and companies around the world. A developer or a company can swipe a credit card and get access to fundamentally unlimited computing power.

By tapping into the power of these cloud computing systems, companies can serve many more customers for much less expense with much less downtime and much greater performance than they could through their own data centers. And as an additional benefit, they don't have to worry about maintaining their own servers.

All the major cloud computing players offer the same basic set of services:

Infrastructure as a Service, or "IaaS," which is the most basic layer of cloud computing. It provides customers with virtual servers and storage.

which is the most basic layer of cloud computing. It provides customers with virtual servers and storage. Platform as a Service, or "PaaS," which is the set of tools and services that make it easier for developers to build applications without worrying about which servers they're running on.

(There's a third layer called "Software as a Service," or SaaS, which refers to applications that run in the cloud like Microsoft's Office 365, Google's G Suite and Salesforce's products for sales and marketing. While these products are powered by the cloud, they're generally note what people mean when talking about "cloud computing.")

The basic game plan for all the cloud-computing vendors is to make their services indispensable to both independent software developers and big companies. Customers might dip their toes in the water of cloud computing with a single app — but as their businesses grow, the cloud service vendors are betting that their cloud usage will also.

Amazon points to something it calls the "virtuous cycle" that has helped drive the cloud industry. The more customers a cloud platform provider signs up, the more servers it can afford to add. The more servers is has, the better it can take advantage of economies of scale and offer customers lower prices for more robust features, including ones likely to appeal to enterprises. The lower the prices and the better the products, the more customers the provider will likely attract — and the more new customers will switch over to the cloud.

Amazon got there first, which is why it's so far ahead

Amazon Web Services sits at the top of the cloud computing mountain. Since its origins as a Jeff Bezos-approved experiment in 2006, it's grown into a mammoth business that generated more than $12 billion in revenue last year.

"AWS invented this market," said Dave Bartoletti, a principal analyst at Forrester Research. "They had a five-year head start before anyone else got their act together."

When AWS first launched, it only offered a basic set of infrastructure services. Customers could get access to virtual servers through a service Amazon called the Elastic Compute Cloud, or EC2. They could also use AWS for file storage, through Amazon Simple Storage Service or S3.

At first, AWS was primarily used by smaller developers as a cheap way to test things or run simple websites. Over time, many of those experimental apps and simple sites grew into popular, widely used services. Even as they did, the companies behind them, including Netflix, Airbnb, and Slack, kept AWS at the core of their offerings.

View photos Andy Jassy, Amazon More