Reader mail: What the heck is this cloud computing stuff, anyway?Marjorie writes: Somebody at work was going on about how information is now going to be stored in clouds. I’m not a total idiot so I realize he did not mean the fluffy white cumulus kind. But I’m enough of an idiot to not really know what this is all about.

Dear Marjorie: Don’t worry—you’re not an idiot. If anything, I should be wearing the dunce cap for not taking a breath and explaining this whole “cloud” thing.

So, here’s the thing. You’ve got your computer on your desk, right? The one with all your files on it, your programs (like Microsoft Word and Excel), your music player (maybe iTunes or Windows Media Player), and your systems files (all the behind-the-scenes stuff that makes Windows and the Mac operating systems do what they do).

All those files are sitting on the hard drive in your system—and we call them “local” files because they’re stored, well, locally. If your Internet connection conks out, you can still open all your local Word documents, music tracks, and photos, because they’re right there in your Mac or PC. Nice—but on the other hand, if you’re working at your office PC and you want to open a specific Word file that’s sitting on your desktop back at home … you’re out of luck.

OK, so that’s the “local” side of the equation. At the opposite end, we’ve got “remote” files—that is, files that are stored not on the PC right in front of you, but on a remote server that’s hundreds or even thousands of miles away. (Don’t worry—we’ve almost reached the “cloud.”)

Now, Marjorie, you probably deal with remote servers all the time without even realizing it. Do you use, say, Gmail or Yahoo! Mail—and do you open and write your email messages from inside a web browser? If so, all those messages you’re sorting through are sitting on a remote server somewhere … or as we say in the industry, they’re up “in the cloud.”

Why "scan and match" will become a key phrase in digital musicWhat’s the advantage of having your email in the cloud? Simple: you can access your messages from any web browser (be it on you PC or phone), whether you’re at home, in the office, or at an Internet cafe. And we’re not just talking email, either. Google, for example, lets you store and even edit Word, Excel, and PowerPoint documents online (with Google Docs), while Apple is getting ready to stream your entire music collection from the cloud with its “iCloud” music service.

Convenient, right? But here’s the thing when it comes the “cloud” (or two things, to be precise):

Number one: You must have an Internet connection to get to your cloud-based email or files. If your home Internet connection conks out and you don’t have your remote, “cloud”-based files stored on a “local” computer, you won’t be able to access them.

Number two: If the “cloud” service you’re using goes on the blink—for example, if someone pulls the plug on Google’s servers, or Apple’s iCloud goes dark thanks to a traffic jam of eager music lovers—you may find yourself unable to access your cloud-based documents, even if your Internet connection is up and running.

Alright, so does that mean that a “local” computer is a safer place for your files and email than the cloud? Well, not necessarily; there’s always a chance that hard drive in your Mac or PC will give up the ghost (and hey, it happens)—in which case, you’ll be pretty happy to have kept at least some of your files safe in the cloud.

So yes—when we talk about the “cloud,” we’re referring to far-flung server warehouses somewhere, all humming away with copies of your files that you can access from anywhere…so long as the servers are happy and you’ve got access to the Internet.

Meanwhile, “local” files are sitting right there on your desktop, laptop, or phone, and you can open them even without an Internet connection—but if your local files are at home and you’re elsewhere, you won’t be able to get to them.

Make sense? Have more questions about the “cloud”? (C’mon, I know you do.) Let me know!