Remember when you used to look up and see things in the clouds? A cumulonimbus Valhalla, or a pirate ship, or a frighteningly real representation of your third-grade teacher? Those were the days. And now there's a new kind of cloud that you just can't get away from. Seems like in everything I read and everyplace I turn, there it is. The cloud. There is no escape. So it's probably a good time to develop a basic understanding of just what this cloud is, along with the major players.

"The cloud" is just slang for an advanced server network that puts a massive amount of information, more than could ever be stored in your home or office, at your Internet-connected fingertips. Entire businesses can run from the cloud. The companies that provide the necessary infrastructure and software to keep the cloud running are called cloud providers. A lot of companies are scrambling for space on the cloud, but there are three players that really stand out to me right now.

No. 1 in the cloud
I never thought of (Nasdaq: AMZN) as a big cloud player until its servers crashed and shut down multiple businesses, including Reddit and Before that headline-grabbing event, I really only thought of Amazon as a place to buy a bunch of random things all at the same time. Turns out that analyst estimates placed Amazon's cloud revenues at upward of $650 million in 2010, and that figure will continue to grow as more companies move to a cloud-based infrastructure. Amazon sells space in the cloud, and now it even has a cloud-based music player. Cue the affectionate nickname: Boss Cloud.

Growing in the cloud
(NYSE: RAX), I know you're in the cloud, and I feel good about you right now for two reasons. First, your cloud-provider revenue is second only to Boss Cloud. Second, you're converting an old shopping mall in San Antonio into your new headquarters and plan to hire 600 people in your Austin office. Growing is good.

You don't have a lot of cash on hand -- $134 million compared with Amazon's $8.76 billion -- but you love me more than any other company in the world, and your customer-service motto, "Fanatical Support," means a lot to me. Knowing that your sales have grown at an average of 30% a year since 2007 and that analysts expect your net income to climb nearly 50% this year doesn't hurt, either.

Knocking on the door
Who's nipping at the heels of Boss Cloud and Rackspace? Yet another company I never expected: Verizon (NYSE: VZ). Seriously, what's Verizon doing in the cloud? This is a company that's supposed to be digging up my street and laying cable for FiOS. Turns out that with the purchase of Terremark at the beginning of the year, Verizon added 13 data centers to its existing stable of 220 and increased its cloud-providing power. Terremark is a leading provider of IT infrastructure, and Verizon is letting it operate as a wholly owned subsidiary. That's excellent news, because before the acquisition, what cloud offerings Verizon did have were routinely criticized. Only time will tell whether Verizon can make the most of its purchase.

Bottom line
As time goes on, you'll continue to read about large companies buying smaller ones in an effort to immediately increase their cloud-provider capacity. Infrastructure isn't the only place to watch, though. The cloud-security sector is also growing by leaps and bounds. Even if you choose to ignore the cloud, keeping an eye on how it affects the companies you follow is a good idea.

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Fool contributor Aimee Duffy doesn't own shares of the companies mentioned in this article. Motley Fool newsletter services have recommended buying shares of and Rackspace Hosting. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.