K2 (like any other Joomla! extension or even the extensions built into the core of Joomla!) interacts with other extensions to the same level com_content (default joomla articles), Virtuemart and more do.

Since you seem to be a new user within the Joomla community, you first have to understand how extensions work, in terms of what a component is and what it can do, what modules and plugins are etc.

Imagine that K2 is like a second "core" to Joomla!, so other developers can easily "retrieve" K2 content and use it however they like, in their own extensions.

All "content" plugins will play nice with K2 content, that means if you install a plugin that converts acronyms to words with a link it will play nice on both joomla core articles and K2.

Hope I covered some of your questions.

Cory Webb wrote a nice article some time ago on joomla jargon: www.howtojoomla.net/2006120741/how-tos/miscellaneous/joomla-jargon - have a look ;)

K2 is there for other extensions to use its content. It acts like com_content, the built in joomla articles component. It's up to other devs to create modules that utilize the richer content produced by K2. So as you can understand, a module that fetches the latest X articles from com_content cannot do the same for K2, unless the developer modifies its code.

Plugins on the other hand don't fall into this case. All content plugins will execute nicely within K2, cause plugins work by nature differently to modules.

Components are like different applications. Again it's up to the developer to hook their component up with K2.

And lastly... We made K2 with a vision to bring better and richer content experience to Joomla! 1.5 - and not wait for 1.6 or 2.0. We "open sourced" it so others can see the code and extend it. So we are providing a new content platform which is GPL and available to all. Can this be restrictive to Joomla! users? I don't think so... ;)

Don't think. Use it first, please.

RocketTheme will at any point create a module to fetch content from K2.

K2 is open source and they are free to do so. Furthermore, we encourage RocketTheme and other designers or developers to do so.

It does not work because it has different specs, not because WE have our slideshow system. I'm sure Andy and his people will produce a K2 version of their modules soon...

That's good news from RocketTheme! :)

This means that the plugin is probably not published or that the plugin's code is restricted to com_content only.