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.

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All of this was possible before through a smartphone's web browser (and Google Sync has been available on Blackberries for months), but if you were looking to push update your phone to various Google-stored information through the iPhone or Windows Mobile, it was pretty much a read-only experience. Now you can treat Google's calendar and contacts like any push service, updating your phone to the cloud in real time.

And I'm way too excited about this development. [Google Sync via lifehacker]

UPDATE: I'd mentioned that Gmail was included. It is not.

Because while Blackberries are historically known for excellent emailing on huge keyboards, their newer SureType (two letters per key) system has turned off many users to smaller models like the Pearl.

But then you see this new patent mockup and you think, ooh, foldout keyboard! Death to SureType! Full QWERTY on the Blackberry Pearl! Unicorns live!

And then you realize that RIM's mockup doesn't add more buttons, it just puts two letters on each key. SureType just gets bigger. [US Patent Office via Engadget Mobile]

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Until now, the only thing that separated the BlackBerry from the iPhone—apart from the iPhone's better, faster and more powerful operating system—was the push email on the BlackBerry. (Well, and the physical keyboard that some people say they could never part with.) I was a CrackBerry addict myself before getting the iPhone, and the only thing I missed (sometimes not really, because it can get very annoying) was the push email.

With iPhone OS 2.0 and MobileMe (or the enterprise connectivity options) the push email difference is completely gone.

The push mail works flawlessly. Even over international connections: to do the cellphone network test I used a Vodafone Spain SIM card running on the Vodafone UK network here in London. Not a single glitch—the thing just worked almost instantly. Knowing that Apple is using Sun Java Messaging Servers, probably paired with Synchronica or Consilient's over-the-air synchronization modules, I'm not surprised. It feels like they have put together a rock-solid operation.

If you couple that with the fact that both consumers and enterprise iPhone users are going to be able to push sync everything, including calendars, address book and web bookmarks, you can see why Research In Motion is going to have a very tough time defending against the Apple juggernaut on software features. The combination of multimedia, consumer and enterprise features on the iPhone, coupled with the flawless Application Store and its user interface, makes any BlackBerry look like a useless brick.

UPDATE: While we love the push email, Ars has some tests that show why the iPhone may not be ready for primetime enterprise.

Jeez, does it take a long time for a cellphone to be approved for US use, or what? Case in point: the Sony Ericsson P990i, which just made it through the labyrinthine gauntlet of the FCC approval process.

In case you've forgotten about this powerful smartphone we introduced to you back in December of last year, it supports the Symbian OS 9.1 and the UIQ 3 platform, it's got a music player on board that supports MP3, AAC and AAC+, and it specializes in push e-mail with a highly functional QWERTY keyboard. Expect to see the Sony Ericsson P990i available stateside next month. – Charlie White

Sony P990i Approved for the USA [Mobilewhack, via Smartfone]

Synchronica, which has its SyncML Gateway, similar to RIM's push email gateway, allows devices like the Ogo to get notified when an email comes in. As opposed to pull email, which means the device needs to go to a server and check periodically whether there's an email available. This causes strain on the server and uses up bandwidth for the client, which is precious, and not to mention costly, for mobile devices. An added bonus to Synchronica's solution (SyncML and Push IMAP) is that it's based on open standards and should be free from the patent issues RIM has been facing.

What does this all mean to you? IXI, the maker of the Ogo, has licensed Synchronica's push email technology, so you can now get a push email device that can also do IM without paying the premium for a BlackBerry. The downside is that the Ogo is still a data-only device, so you'll have to have a separate cell phone if you want to receive calls. – Jason Chen

Ogo is the Blackberry-killer [The Inquirer via BlackBerry Cool]

[Thanks, Spungle]

If you put off purchasing the Treo 700w on Verizon because of of its tragic, pointless lack of push email support, rejoice! Palm and Verizon released the 1.10 update for the 700w today, adding push email capability to it among other things and finally making this smartphone, well, smart. Here's the list of 1.10 enhancements:

• Includes Microsoft®'s Messaging and Security Feature Pack (MSFP) with Direct Push Technology for automatic wireless synchronization of email, calendar, contacts and, now, tasks
• Enhances email capabilities for more support of push email solutions, such as WirelessSync and GoodLink, and of synchronization capabilities, such as the ability to maintain an "always on" data connection after POP or IMAP email synchronization and the ability to auto-synchronize all email accounts based on user setting.
• Updated memory management
• Pictures and Videos enhancements
• New Wireless Manager provides an updated interface for turning wireless radios on and off on your 700w smartphone

Treo 700w Updater 1.10 for Verizon Wireless smartphones [Palm Support, via Alpha Blog]
Treo 700w Launched, Verizon Has It [Gizmodo]