Well, push describes a lot of things. Push is simply an action. Versus, say, pulling. Maybe that's horribly abstract, so try this: If information shows up on your phone or neural implant or messaging program without you (or your wares) asking for it—that's push. The info is pushed to you, versus you pulling it from the source. There are tons of ways push can be (and is) used.

Email's a pretty good starting point for grasping the difference between push and the other stuff. You probably know good ol' POP3—you log into your mail server and pull down new messages. Maybe it's on a frequent schedule, so it feels automatic, even instant, but you're still reaching out to the mail server every time to check and see if there's new mail to download.

IMAP is a little fancier than POP, where all of your folders and email are the same on all of your computers, phones and other gadgets, and any change you make on one shows up on the other, since it's all happening on a remote server somewhere. But with the standard setup, it's still the same deal—your mail program has to log in, see what's new, and pull it down. IMAP does have a pretty neat trick though, an optional feature called IMAP IDLE, that does push pretty well—it's what the Palm Pre uses for Gmail, for instance. Essentially, with IMAP IDLE, the mail server can tell whatever mail app that you've got new messages waiting, without you (or your app) hammering the refresh button over and over. When the app knows there's new messages, it connects and pulls them down, so it gives you just about the speed of push, without matching the precise mechanism.

While different systems do things differently (obvs), what true push services have in common is that they generally insert a middleman between you and the information source.

RIM's setup for the BlackBerry is probably the most sophisticated. When your BlackBerry registers with the carrier (which has to support BlackBerry), the details are handed to RIM's network operating center, so the NOC knows where to send your mail. The NOC watches your mail server, keeps tabs on the phone's location, and pushes email through to your phone whenever you get new stuff.

What makes it push is that your phone's not actually polling a server for new messages to pull—it only receives them when they hit your inbox, and are then pushed to your phone by RIM's servers. This means you save a lot of battery life that'd be wasted by making the phone constantly hit the servers for updates. The flipside is that when RIM's servers blow up, you don't get email, since it's all routed through their system—hence the other panic that grips dudes in suits once every few months lately.

The other biggie is Microsoft, who has Direct Push, part of Exchange's ActiveSync. It's architected a little bit differently, so it doesn't need the precise kind of data about where your phone is that RIM's NOCs do: The phone or whatever you've got sends an HTTPS with a long lifespan to the Exchange server—if new mail arrives before it dies, the Exchange tells your device there's new stuff, so it should start a sync. After it syncs, the device sends out another long HTTPS request, starting it all over again.

Apple's weak-sauce substitute for multitasking works pretty similarly: The developer has something its wants to send an iPhone, when its application isn't actually running, like an IM. It sends the notification to Apple's push servers, which send the notification to the phone through a "persistent IP connection" the phone maintains with the servers. This connection, which is only maintained when push notifications are turned on, is needed to locate the phone, but still doesn't draw as much power as constantly pinging the mail server.

Of course, those aren't the only push systems around, and it's only getting more and more important as stuff gets shifted to the cloud. We haven't mentioned Android and Google Chrome, but both utilize push (or will) in different ways. Suffice it to say, Google Sync will soon be a major player in this game. But basically, all kinds of different data can be pushed—calendars, contacts, browser data, hell, even IM is a kind of push—and they all work more or less the same broad way. Just don't ask us why there isn't push Gmail on the iPhone yet.

Still something you wanna know? Send questions about pushing, shoving and pancake massacres to tips@gizmodo.com, with "Giz Explains" in the subject line.

HELIO LAUNCHES MAIL FOR MICROSOFT EXCHANGE

Wirelessly Sync Ocean with Microsoft® Office Outlook® Email, Calendar and Contacts

LOS ANGELES, CA - July 25, 2007 - Helio Ocean's expansive messaging capabilities just got more versatile with the launch of Mail for Microsoft Exchange. Adding to Ocean's already comprehensive messaging line-up including a single hub for all text messages, picture messages, Instant Messages and emails from the major portals and ISPs, Helio members can now mix business with pleasure through Mail for Microsoft Exchange. This new application lets users wirelessly synchronize Microsoft® Office Outlook® email, calendar and contacts from their companies' Microsoft® Exchange Server so they can use Ocean to keep in touch with friends and family, as well as staying on top of business.
"Ocean has already made staying in touch with friends easier than ever with the ultimate messaging dashboard for all email, IM, picture and text messages, something nobody has ever done before," said Doug Britt, Sr. Director of Content and Messaging Services at Helio. "Now we're bringing the business user into the fold with the addition of corporate email, calendar and contacts, all from the same great messaging interface. Combined, this solidifies Ocean as an ideal device for keeping in touch with friends, family and business associates."

Business + Pleasure
Mail for Microsoft Exchange is Helio's new downloadable client that uses the Microsoft® Exchange ActiveSync® protocol to let users remotely synchronize and access business email, contacts and calendar data from their corporate Exchange Server. Ocean users can wirelessly download Mail for Microsoft Exchange to their device and after a brief set up, send and receive email, create and send calendar appointments and access corporate contact lists. Once Mail for Microsoft Exchange is downloaded, it is also easily accessible through Ocean's messaging home screen aside the full suite of Ocean's messaging capabilities.

Helio will also soon launch Helio File Viewer in conjunction with Mail for Microsoft Exchange. When available, Helio File Viewer will allow users to view documents including .doc, .ppt, .xls, and .pdf files.