Do you have an e-mail account, such as Hotmail, gMail, Yahoo, where you log into a web browser to check your mail? And you can use a friend's computer to check it, or a computer pretty much anywhere? Your e-mail is in the cloud. Sort-of.
Cloud computing is a form of energy-efficient, technology-efficient computing that is gaining some popularity. Can you imagine how much electricity it would take if everyone with an e-mail address had to leave their computer on 24 hours a day, 7 days a week if they wanted it to be delivered?
Some of you may use an e-mail system that deletes your e-mail when you download it to your computer (this is called a POP3 mail service, by the way). That was a lot more popular when hard drives were measured in megabytes and not gigabytes... now technology is so inexpensive, there's less justification for having to download e-mail you're planning to keep. Wouldn't it be nice to access your e-mail on the road, anywhere, instead of having to load it from the exact computer you downloaded it with?
For those of you who don't remember a time your e-mail was only on one computer, congratulations! It was surely a hassle. With web-based e-mail services, you typically leave the mail you want to keep on a server somewhere.
Now, do you care where that computer is, what software it's running? If it's reliable, secure, and does what you need it to do, you're less concerned with the exact details of how it happens. Cloud computing works a lot like this, except for all sorts of uses, not just for e-mail!
Cloud computing, in its perfect form, is fairly transparent to the user. The less you have to worry about, the better. The people who administer the server most definitely care about the details, to you it just works.
Okay, so now you know the basic idea of cloud computing. But how is it energy-efficient and technology-efficient?
This is the way we often computed before the cloud, but do you use your computer 100% of the time? Or are there times you are just reading an e-mail message and it's doing pretty much nothing, yet still drawing electricity from the wall?
Some servers run at 100% all the time. But many servers don't. In cloud computing, we start by virtualizing the servers, meaning we combine the needs of several companies into a small number of servers (in this example, we're taking 3 servers into one hardware server). Imagine the first company buys a server with a little bit more capacity, and rents out the extra to the other two companies. Now you have this:
This is an oversimplification, cloud computing is much more complicated than this, but it's a good way to start visualizing it. We're using less computers and less electricity to accomplish the same goal: a great reliable service to the customer.