Google Wave despite its criticisms has always been an intriguing concept, especially the way the system was capable of being augmented with extensions and robots.
Unfortunately for those brave enough to explore Google Wave, there was no central place to find such extensions, and even worst, often installing such extensions meant entering a scary looking URL into an obscure place to insert a gadget.
For most people this is quite a turn-off, and they will surely welcome the new Extensions Galley which has been introduced. The Extension gallery is just another folder containing a collection of Waves each containing a single extension with its description and installer.
An installed extension will appear in your message toolbar amongst other buttons for Bold, Italics etc. The extensions gallery currently only includes Gadgets, Robots are conspicuously missing.
For those who missed out on Google Wave extensions, Gadgets are small applets which can be inserted into a Wave conversation and can be used by the participants in that Wave. A Gadget could be a simple applet such as the Yes/No/Maybe Gadget which allows you to gets peoples' responses (from yes, no or maybe) for any discussion -- such as going to watch a film. A more extensive Pollo Gadget allows you to conduct a poll. Then again there are extensions such as Phone Conference.
Robots on the other hand, are virtual participants in a Wave, and can modify the very contents of a Wave. For example, a translation robot could automatically translate the content of a wave, a Twitter Gadget would tweet any messages you create in a wave, and update it with replies etc. Recently Google had overhauled their Robots API with a new v2 release which makes Robots more powerful and optimized.
The extension gallery currently contains only a few popular extensions which have been tested by Google, and some of the ones -- such as Bloggy, the blogging robot -- demonstrated at the Google I/O event, when Google Wave was introduced, are absent as they are not "ready for prime time". While Google Wave is not longer as much in hype now as it was immediately following its launch, work on this amazing technology continues in the background.
Google Wave is powerful indeed, however for those unable to wield that power, it seems like an overkill simply to communicate. Google will need to address quite a few of it's quirks and complaints before they can move this from its Preview state. If Wave is to be the future of communication it will need to be more intuitive to use -- if you need a tutorial to understand how to communicate with an application, something needs to be fixed.