You wouldn’t put it past them, and now they’ve done it; Google has reinvented email.

The news has reached most people by now, but just in case you’ve been living under a rock for the past few months, I’ll start out with an – admittedly oversimplified – explanation. Because that’s the thing with Google Wave: everybody knows it’s cool, but few people really know how to explain it.

The ‘old’ concept of email is still pretty much based on paper post. People sending static messages to other people. Everything is based on the process of sending and receiving. When working in the group, this poses a number of problems. For example, Reply to All creates a new static message, and again sends duplicates to everyone involved.

In contrast, Google Wave creates one dynamic copy, and hosts it in the clouds. Everybody reads one and the same message. And that’s just the core idea. People can edit the message (hence, dynamic) and even put their reply right in the middle of it! Unless turned off, people can read up as you type, and you can edit messages with multiple people at the same time. That, dear people, is Google Wave.

Learn more about Google wave in this 1 hour and 20 minute looooong video.

Another important aspect of Google Wave are the gadgets. These are in fact small web-applications that can be embedded in a wave. When you first start using Google, you’ll notice the two that are present by default; the Yes/No/Maybe- and Map Gadget. But anyone with a bit of programming knowledge can create their own. Below are five that everyone should add.

Invity

Ever noticed how time-consuming it can be to create a multi-person Wave? Instead of adding them all manually, it’d be real nice to have a decent grouping feature. Until then, we’ve got Invity.

Invity is actually a robot (yes, as in a chat bot), but it’s more useful than many gadgets. Instead of installing, just add pw-invity@appspot.com on Wave.

To create a group of contacts, add them to a wave together with Invity. You can then create a new group. The next time you want to create a Wave, simply add the Invity, and invite everyone over! Easy as that.

Napkin

Napkins are known to serve as an outlet for creativity, and now you’ve got one in Wave. You can use it to draw a quick doodle beneath your message, or even draw simultaneously with your friends.

Ribbit Conference Gadget

This begins to show how far Wave has left the conventional email threads behind. With Ribbit’s gadget (free for now, but probably not forever), you have VoIP in your inbox. You can call your friends from a Wave and even create a conference.

iFrame

No pretty picture here, but any one would fit. An iFrame allows you to open a window to any page on the internet. You can use it to add virtually anything; a flash app, the latest Dilbert cartoon, a stock gadget — whatever you can find online.

Here are the Gadget XML and Installer XML. You can use these links to respectively use, or install the gadget in Google Wave.

Know any other cool Google Wave gadgets or robots? Tell us your favorite in the comment!