Previously you could just sync your Google contacts and calendars, but now finally it supports Gmail as well, allowing you to be notified instantly when you get a new email. Push Gmail via Google Sync works on the iPhone as well as in Windows Mobile and Symbian. [Google Mobile Blog via TechCrunch]

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 centre, 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 utilise 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, browser data, hell, even IM is a kind of push—and they all work more or less the same broad way.

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

The E75 (and all upcoming Nokia Messaging enabled phones) will also access corporate email through Microsoft Exchange or Lotus Notes. The phone supports up to 10 different email accounts, and like the E71, you can switch between Work and Personal modes to keep yourself sane on the weekends.

The E75 will hit shelves today, and has an RRP of $979. We’ve got a unit here to play around with, so stay tuned for some thoughts over the next few days

[Nokia]

The Pronto shares the same $US20 monthly plan as the original Peek, but on top of unlimited push emailing, that plan also supports unlimited text messaging. The Pronto’s software is also a bit more advanced, including the ability to check out documents and PDFs, as opposed to just pictures.

The Pronto is available now, but unlike the original, it’s only in black (they call it grey). [Peek]

UPDATE: Over on the Peek messageboards, one user claims that the old Peek will receive the same software soon. Consider that unconfirmed, but it seems likely enough.

UPDATE 2: Future Peek Classics will no longer have SMS.

Gawker Media polls require Javascript; if you’re viewing this in an RSS reader, click through to view in your Javascript-enabled web browser.

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. 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) that difference is completely gone.

The push mail works flawlessly. Even over international connections: to do the mobile phone 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 synchronisation 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. 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.