What the hell is the cloud? Well, it's not those white puffy things in the sky. Wait, maybe it is. The cloud, in it's simplest form is a repository of computer stuff that is not sitting at your business or house. Let me expand - iCloud for example, is Apple's cloud offering and it allows users of Apple products to backup and synchronize their songs, pictures, apps, games to all devices, wirelessly. Every time you turn on your iPhone, Mac or iPad it send your latest purchases, songs, videos and/or pictures to an Apple datacenter. So if you turn on your iPhone and buy a new app, the next time you fire up your iPad it will magically be there. This is all protected in Apple's cloud with your Apple ID for your security. If you lose your iPhone at least you won't lose that cool video of your dog you took and your custom ring tones and your 10 GB of songs. They will magically be synchronized back to your new iPhone when you can actually afford to buy one. As an aside to that - if your Apple ID password is insertpetnamehere1 then CHANGE IT. It is not secure. Anyone can figure that out.
Cloud in relation to business is essentially the same concept as Apple's iCloud except with additional options. Instead of synchronizing my songs in the cloud, as a business, I'm storing my data there. This is called Cloud Storage or Cloud Backup. All kinds of companies sell online backup solutions; Jungle Disk, Mozy, and Carbonite just to name a few. These online backup companies can be used to backup the server of a small business or your home PC. Doesn't matter. You pay by the Gigabyte. That's the beauty of cloud services. They are mostly a sort of pay-as-you-go or pay by use model.
As we go higher up in business size we get in to even more types of cloud offerings. There is SaaS, PaaS, IaaS just to name a few. The acronym is blank as a service, where I is Software, P is platform and I is infrastructure. You can probably come up with many more blanks but these are the big 3. The best example of Software as a Service is Microsoft Office 365. It's all of Microsoft office offerings, Word, Excel, Powerpoint, Outlook, Email but not living on your computer that you or your company loaded on your desktop with a CD, it lives in the cloud. When you launch a Word document, it's launched from one of Microsoft's humongous datacenters.
Platform as a Service is the ability of a software developer or company to "spin" up a server in minutes in the cloud, test their software over a course of time, then turn it off. They pay for only that time the server was in use. Amazon's EC2 is an example of this. (EC2 = Elastic Compute Cloud)
Infrastructure as a Service is for an IT department of a company to deploy servers (normally virtualized), business applications and other resources to it's users but the actual equipment isn't in a server room in the office, it's in the cloud. This hot new IT offering is supposed to save money and save on personnel costs. Just think if companies didn't have server rooms with equipment in them and everything was in the cloud. You could fire all your IT people and they would be replaced by one bill from the cloud provider where one guy walks around a huge datacenter managing 100's of companies servers. Concerned about security? You should be. Concerned for your job? You should be.
My favorite cloud computing term - Cloud Washing -- Where a company re-brands their old application or product offering as Cloud something, making it look like its a cloud offering to capitalize on the buzz.